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SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 (d) OF

THE SECURITIES EXCHANGE ACT OF 1934

BANCFIRST CORPORATION

(Exact name of registrant as specified in its charter)

101 North Broadway, Oklahoma City, Oklahoma 73102

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code: (405) 270-1086

Securities registered pursuant to Section 12(b) of the Act: None

Securities registered pursuant to Section 12(g) of the Act:

Common Stock, $1.00

Par Value Per Share

(Title of Class)

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ¨ No x

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes ¨ No x

Indicate by check mark whether the registrant (1) has filed all reports required by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes x No ¨

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, or a non-accelerated filer. See definition of “accelerated filer and large accelerated filer” in Rule 12b-2 of the Exchange Act.

            Large accelerated filer ¨             Accelerated filer x             Non-accelerated filer ¨

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ¨ No x

The aggregate market value of the Common Stock held by nonaffiliates of the registrant computed using the last sale price on June 30, 2005 was approximately $316,415,000.

As of February 28, 2006, there were 15,667,092 shares of Common Stock outstanding (post stock split adjustment).

DOCUMENTS INCORPORATED BY REFERENCE:

Portions of the Proxy Statement for the May 25, 2006 Annual Meeting of Stockholders of registrant (the “2006 Proxy Statement”) to be filed pursuant to Regulation 14A are incorporated by reference into Part III of this report.

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FORM 10-K

CROSS-REFERENCE INDEX

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PART I

Item 1. Business.

General

BancFirst Corporation (the “Company”) is an Oklahoma business corporation and a financial holding company under Federal law. It conducts virtually all of its operating activities through its principal wholly-owned subsidiary, BancFirst (the “Bank” or “BancFirst”), a state-chartered bank headquartered in Oklahoma City, Oklahoma. The Company also owns 100% of the common securities of BFC Capital Trust I and BFC Capital Trust II, both Delaware Business Trusts, 75% of Century Life Assurance Company, an Oklahoma chartered insurance company, 100% of Council Oak Partners LLC, an Oklahoma limited liability company engaging in investing activities, 100% of Wilcox & Jones, Inc., an Oklahoma business corporation operating as an independent insurance agency, and 100% of Park State Bank, a state-chartered bank headquartered in Nicoma Park, Oklahoma that the Company acquired in December 2005.

The Company was incorporated as United Community Corporation in July 1984 for the purpose of becoming a bank holding company. In June 1985, it merged with seven Oklahoma bank holding companies that had operated under common ownership and the Company has conducted business as a bank holding company since that time. Over the next several years the Company acquired additional banks and bank holding companies, and in November 1988 the Company changed its name to BancFirst Corporation. Effective April 1, 1989, the Company consolidated its 12 subsidiary banks and formed BancFirst. The Company has continued to expand through acquisitions and de-novo branches. BancFirst currently has 83 banking locations serving 43 communities throughout Oklahoma.

The Company’s strategy focuses on providing a full range of commercial banking services to retail customers and small to medium-sized businesses both in the non-metropolitan trade centers of Oklahoma and the metropolitan markets of Oklahoma City, Tulsa, Lawton, Muskogee, Norman and Shawnee. The Company operates as a “super community bank”, managing its community banking offices on a decentralized basis, which permits them to be responsive to local customer needs. Underwriting, funding, customer service and pricing decisions are made by Presidents in each market within the Company’s strategic parameters. At the same time, the Company generally has a larger lending capacity, broader product line and greater operational efficiencies than its principal competitors in the non-metropolitan market areas (which typically are independently-owned community banks). In the metropolitan markets served by the Company, the Company’s strategy is to focus on the needs of local businesses that are not served effectively by larger institutions.

The Bank maintains a strong community orientation by, among other things, appointing selected members of the communities in which the Bank’s branches are located to a local consulting board that assists in introducing prospective customers to the Bank and in developing or modifying products and services to meet customer needs. As a result of the development of broad banking relationships with its customers and the convenience and service of the Bank’s multiple offices, the Bank’s lending and investing activities are funded almost entirely by core deposits.

The Bank centralizes virtually all of its back office, support and investment functions in order to achieve consistency and cost efficiencies in the delivery of products and services. The Bank provides centralized services such as data processing, operations support, bookkeeping, accounting, loan review, compliance and internal auditing to the Bank’s community banking offices to enhance their ability to compete effectively. The Bank also provides centrally certain specialized financial services that require unique expertise. The community banking offices assist the Bank in maintaining its competitive position by actively participating in the development of new products and services needed by their customers and in making desirable changes to existing products and services.

The Bank provides a wide range of retail and commercial banking services, including: commercial, real estate, agricultural and consumer lending; depository and funds transfer services; collections; safe deposit boxes; cash management services; retail brokerage services; and other services tailored for both individual and corporate

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customers. The Bank also offers trust services and acts as executor, administrator, trustee, transfer agent and in various other fiduciary capacities. Through its Technology and Operations Center, the Bank provides item processing, research and other correspondent banking services to financial institutions and governmental units.

The Bank’s primary lending activity is the financing of business and industry in its market areas. Its commercial loan customers are generally small to medium-sized businesses engaged in light manufacturing, local wholesale and retail trade, services, agriculture, and the energy industry. Most forms of commercial lending are offered, including commercial mortgages, other forms of asset-based financing and working capital lines of credit. In addition, the Bank offers Small Business Administration (“SBA”) guaranteed loans through BancFirst Commercial Capital, a division established in 1991.

Consumer lending activities of the Bank consist of traditional forms of financing for automobiles, residential mortgage loans, home equity loans, and other personal loans. In addition, the Bank is one of Oklahoma’s largest providers of guaranteed student loans.

The Bank’s range of deposit services include checking accounts, NOW accounts, savings accounts, money market accounts, sweep accounts, club accounts, individual retirement accounts and certificates of deposit. Overdraft protection and autodraft services are also offered. Deposits of the Bank are insured by the Bank Insurance Fund administered by the Federal Deposit Insurance Corporation (“FDIC”). In addition, certain Bank employees are licensed insurance agents qualified to offer tax deferred annuities.

Trust services offered through the Bank’s Trust and Investment Management Division (the “Trust Division”) consist primarily of investment management and administration of trusts for individuals, corporations and employee benefit plans. Investment options include collective equity and fixed income funds managed by the Trust Division and advised by nationally recognized investment management firms.

BancFirst has the following principal subsidiaries: Council Oak Investment Corporation, a small business investment corporation; Citibanc Insurance Agency, Inc., a credit life insurance agency, which in turn owns BancFirst Agency, Inc., an insurance agency; Lenders Collection Corporation, which is engaged in collection of troubled loans assigned to it by BancFirst, and BancFirst Community Development Corporation, a certified community development entity. All of these companies are Oklahoma corporations. BancFirst also owns 50% of PremierSource LLC, an Oklahoma limited liability company providing employee benefit plan and insurance products and services.

The Company had approximately 1,400 full-time equivalent employees as of December 31, 2005 and 1,375 full-time equivalent employees at December 31, 2004. Its principal executive offices are located at 101 North Broadway, Oklahoma City, Oklahoma 73102, telephone number (405) 270-1086.

Market Areas and Competition

The banking environment in Oklahoma is very competitive. The geographic dispersion of the Company’s banking locations presents several different levels and types of competition. In general, however, each location competes with other banking institutions, savings and loan associations, brokerage firms, personal loan finance companies and credit unions within their respective market areas. The communities in which the Bank maintains offices are generally local trade centers throughout Oklahoma. The major areas of competition include interest rates charged on loans, interest rates paid on deposits, levels of service charges on deposits, completeness of product line and quality of service.

Management believes the Company is in an advantageous competitive position operating as a “super community bank.” Under this strategy, the Company provides a broad line of financial products and services to small to medium-sized businesses and consumers through full service community banking offices with decentralized management, while achieving operating efficiency through product standardization and

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centralization of processing and other functions. Each full service banking office has senior management with significant lending experience who exercise substantial autonomy over credit and pricing decisions, subject to a tiered approval process for larger credits. This decentralized management approach, coupled with continuity of service by the same staff members, enables the Bank to develop long-term customer relationships, maintain high quality service and respond quickly to customer needs. The majority of its competitors in the non-metropolitan areas are much smaller, and neither offer the range of products and services nor have the lending capacity of BancFirst. In the metropolitan communities, the Company’s strategy is to be more responsive to, and more focused on, the needs of local businesses that are not served effectively by larger institutions.

Marketing to existing and potential customers is performed through a variety of media advertising, direct mail and direct personal contacts. The Company monitors the needs of its customer base through its Product Development Group, which develops and enhances products and services in response to such needs. Sales, customer service and product training are coordinated with incentive programs to motivate employees to cross-sell the Bank’s products and services.

Control of the Company

Affiliates of the Company beneficially own approximately 53% of the outstanding shares of the Company’s common stock outstanding. Under Oklahoma law, holders of a majority of the outstanding shares of common stock are able to elect all of the directors and approve significant corporate actions, including business combinations. Accordingly, the affiliates have the ability to control the business and affairs of the Company.

Supervision and Regulation

Banking is a complex, highly regulated industry. The Company’s growth and earnings performance and those of the Bank can be affected not only by management decisions and general and local economic conditions, but also by the statutes administered by, and the regulations and policies of, various governmental regulatory authorities. These authorities include, but are not limited to, the Board of Governors of the Federal Reserve System (the “Federal Reserve Board”), the Federal Deposit Insurance Corporation (the “FDIC”) and the Oklahoma State Banking Department. The effect of these statutes, regulations, and policies and any changes to any of them can be significant and cannot be predicted.

The primary goals of the bank regulatory framework are to maintain a safe and sound banking system and to facilitate the conduct of sound monetary policy. In furtherance of these goals, Congress has created several largely autonomous regulatory agencies and enacted numerous laws that govern banks, bank holding companies and financial holding companies, and the banking industry. This regulatory framework is intended primarily for the protection of a financial institution’s depositors, rather than the institution’s shareholders and creditors. The following discussion describes certain of the material elements of the regulatory framework applicable to bank holding companies and financial holding companies and their subsidiaries and provides certain specific information relevant to the Company, which is both a bank holding company and a financial holding company. The descriptions are qualified in their entirety by reference to the specific statutes and regulations discussed.

General

As a financial holding company and a bank holding company, the Company is regulated under the Bank Holding Company Act of 1956 (the “Bank Holding Company Act”), as amended by the 1999 financial modernization legislation known as the Gramm-Leach-Bliley Act, as well as other federal and state laws governing the banking business. The Gramm-Leach-Bliley Act preserves the role of the Federal Reserve Board as the umbrella supervisor for both financial holding companies and bank holding companies while at the same time incorporating a system of functional regulation designed to take advantage of the strengths of the various federal and state regulators. In particular, the Gramm-Leach-Bliley Act replaces with more limited exemptions the broad exemption from Securities and Exchange Commission (“SEC”) regulation that banks previously enjoyed, and it reaffirms that states are the regulators for the insurance activities of all persons who conduct such activities, including banks.

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The Company’s banking subsidiaries are also subject to regulation and supervision by various regulatory authorities, including the Oklahoma State Banking Department and the FDIC. At December 31, 2005, the Company had two banking subsidiaries: BancFirst and Park State Bank. Park State Bank was merged with and into BancFirst in February 2006. The Company and its subsidiaries and affiliates are also subject to various other laws and regulations and supervision and examination by other regulatory agencies, all of which directly or indirectly affect the operations and management of the Company and its ability to make distributions to stockholders.

Additionally, the Company’s common stock is registered with the SEC under Section 12(g) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Consequently, the Company is subject to the information, proxy solicitation, insider trading and other restrictions and requirements of the SEC under the Exchange Act and, as a company whose shares are traded on the Nasdaq National Market System, the rules of the Nasdaq Stock Market.

Financial Holding Company Regulation

In general, the Bank Holding Company Act limits the business of bank holding companies that are financial holding companies to banking, managing or controlling banks, performing certain servicing activities for subsidiaries, and as a result of the Gramm-Leach-Bliley Act amendments to the Bank Holding Company Act, engaging in any activity, or acquiring and retaining the shares of any company engaged in any activity, that is either (1) financial in nature or incidental to such financial activity (as determined by the Federal Reserve Board in consultation with the Secretary of the Treasury, or (2) complementary to a financial activity and does not pose a substantial risk to the safety and soundness of depository institutions or the financial system generally (as solely determined by the Federal Reserve Board). Activities that are financial in nature include securities underwriting and dealing, insurance underwriting and merchant banking investment activities. They also include activities that the Federal Reserve Board had previously determined, by order or regulation in effect prior to the enactment of the Bank Holding Company Act, to be so closely related to banking or managing or controlling banks as to be a proper incident thereto. A financial holding company may conduct any of these designated activities so long as the financial holding company notifies the Federal Reserve Board within 30 days after the financial holding company commences such activities or acquires a company that engages in such activities. If a financial holding company wishes to engage in activities that are “financial in nature or incidental to a financial activity” but not yet specifically authorized by the Federal Reserve Board, the financial holding company must file an application with the Federal Reserve Board. If both the Federal Reserve Board and Department of Treasury approve the application, the financial holding company may commence the new activity. The Federal Reserve Board may also approve a new activity that is complementary to a financial activity, but the financial holding company must make an additional showing that the activity does not pose a substantial risk to the safety and soundness of depository institutions or the financial system generally.

In order for a bank holding company to engage in the broader range of activities that are permitted by the Bank Holding Company Act for bank holding companies that are also financial holding companies, (1) all of its depository institutions must be well-capitalized and well-managed and (2) it must file a declaration with the Federal Reserve Board that it elects to be a “financial holding company”. In addition, to commence any new activity permitted by the Bank Holding Company Act and to acquire any company engaged in any new activities permitted by the Bank Holding Company Act, each insured depository institution of the financial holding company must have received at least a “satisfactory” rating in its most recent examination under the Community Reinvestment Act. The Company’s election to become a financial holding company became effective in March 2000.

Bank Holding Company Act and other Applicable Laws

Bank Holding Company Regulation

In addition to being a financial holding company, the Company remains a bank holding company and, as such, is regulated under the Bank Holding Company Act and is subject to the supervision of the Federal Reserve

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Board. Under the Bank Holding Company Act, bank holding companies that are not financial holding companies generally may not acquire the ownership or control of more than 5% of the voting shares, or substantially all the assets, of any company, including a bank or another bank holding company, without the Federal Reserve Board’s prior approval. No approval under the BHCA is required, however, for a bank holding company already owning or controlling 50% of the voting shares of a bank to acquire additional shares of such bank.

Bank holding companies generally may engage only in banking and other activities that are determined by the Federal Reserve Board to be closely related to banking. The Federal Reserve Board has by regulation determined that such activities include operating a mortgage company, finance company, credit card company or factoring company; performing certain data processing operations; servicing loans and other extensions of credit; providing investment and financial advice; acting as an insurance agent for certain types of credit-related insurance; owning and operating savings and loan associations; and leasing personal property on a full pay-out, nonoperating basis. A bank holding company that does not qualify as a financial holding company is generally limited in the types of activities in which it may engage to those that the Federal Reserve Board had recognized as permissible for bank holding companies prior to the date of enactment of the Gramm-Leach-Bliley Act.

Control Acquisitions

Subject to certain exceptions, the Change in Bank Control Act (the “Control Act”) and regulations promulgated thereunder by the Federal Reserve Board require any person acting directly or indirectly, or through or in concert with one or more persons, to give the Federal Reserve 60 days’ written notice before acquiring control of a bank holding company. Transactions which are presumed to constitute the acquisition of control include the acquisition of any voting securities of a bank holding company having securities registered under section 12 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), if, after the transaction, the acquiring person (or persons acting in concert) owns, controls or holds with power to vote 25% or more of any class of voting securities of the institution. The acquisition may not be consummated subsequent to such notice if the Federal Reserve Board issues a notice within 60 days, or within certain extensions of such period, disapproving the same.

Interstate Banking and Branching

Pursuant to the Riegle-Neal Interstate Banking and Branching Efficiency Act of 1994 (the “Interstate Banking and Branching Act”), a bank holding company may acquire banks in states other than its home state without regard to the permissibility of such acquisitions under state law, but subject to any state requirement that the bank has been organized and operating for a minimum period of time, not to exceed five years, and the requirement that the bank holding company, prior to or following the proposed acquisition, controls no more than 10 percent of the total amount of deposits of insured depository institutions in the United States and no more than 30 percent of such deposits in that state (or such lesser or greater amount set by state law). Legislation passed by the Oklahoma legislature in 2000 eliminated the previously existing requirement that Oklahoma banks be in existence for a minimum of five years before being acquired by, or merged into, another bank, or acquired by an existing bank holding company, and increased the state “deposit cap” from 15% to 20%, with the result that a business combination involving Oklahoma-chartered banks may not result in the control by the combined institution of more than 20% of the total deposits of insured depositary institutions located in Oklahoma.

Subject to certain restrictions, the Interstate Banking and Branching Act also authorizes banks to merge across state lines, thereby creating interstate branches, without regard to whether such transactions are prohibited by the law of any state, unless the home state of one of the banks had “opted out” of interstate branching by enacting specific legislation prior to June 1, 1997, in which case out-of-state banks would generally not be able to branch into that state, and banks headquartered in that state would not be permitted to branch into other states. Oklahoma elected to “opt-in” to interstate branching effective May 1997. Furthermore, pursuant to the Interstate Banking and Branching Act, a bank may open new branches in a state in which it does not already have banking operations if such state enacts a law permitting such de novo branching. Oklahoma law permits de novo branching for state-chartered banks and for out-of-state banks where the state of the bank seeking to establish the

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branch also permits it. Accordingly, while Oklahoma state-chartered banks such as BancFirst are able to establish an unlimited number of de novo branches in Oklahoma, out-of-state banks that are chartered in states with reciprocal de novo branching provisions are now able to establish new branches in Oklahoma to the same extent as formerly favored state-chartered banks.

Support for Bank Subsidiaries

The Federal Reserve Board has issued regulations under the Bank Holding Company Act that require a bank holding company to serve as a source of financial and managerial strength to its subsidiary banks. Pursuant to such regulations, the Federal Reserve Board may require the Company to stand ready to use its resources to provide adequate capital funds to its banking subsidiaries during periods of financial stress or adversity. Under the Federal Deposit Insurance Company Improvement Act of 1991 (“FDICIA”), a bank holding company is required to guarantee the compliance of any insured depository institution subsidiary that may become “undercapitalized” (as defined in the statute) with the terms of any capital restoration plan filed by such subsidiary with its appropriate federal banking agency, up to specified limits. See “—FDICIA and Related Regulations,” below. Under the Bank Holding Company Act, the Federal Reserve Board has the authority to require a bank holding company to terminate any activity or relinquish control of a nonbank subsidiary (other than a nonbank subsidiary of a bank) upon the Federal Reserve Board’s determination that such activity or control constitutes a serious risk to the financial soundness and stability of any bank subsidiary of the bank holding company.

Capital Adequacy Guidelines

The Federal Reserve Board, the Comptroller and the FDIC have issued substantially similar risk-based and leverage capital guidelines applicable to United States banking organizations. In addition, these regulatory agencies may from time to time require that a banking organization maintain capital above the minimum levels, whether because of its financial condition or actual or anticipated growth. The risk-based guidelines of the FDIC, the regulatory agency with oversight over state nonmember banks such as the Bank, define a three-tier capital framework. Core, or “Tier 1,” capital, consists of common and qualifying preferred stockholders’ equity, less certain intangibles and other adjustments. Supplementary, or “Tier 2,” capital includes, among other items, certain other debt and equity investments that do not qualify as Tier 1 capital. Market risk, or “Tier 3,” capital, includes qualifying unsecured subordinated debt. The sum of Tier 1 and Tier 2 capital less investments in unconsolidated subsidiaries represents qualifying total capital. Risk-based capital ratios are calculated by dividing Tier 1 and total capital by risk-weighted assets. Assets and off-balance sheet exposures are assigned to one of four categories of risk-weights, based primarily on relative credit risk. The minimum Tier 1 capital ratio is 4% and the minimum total capital ratio is 8%.

Applicable banking regulations also require banking organizations such as the Bank to maintain a minimum “leverage ratio” (Tier 1 capital to adjusted total assets) of 3%. The principal objective of this measure is to place a constraint on the maximum degree to which banks can leverage their equity capital base. These ratio requirements are minimums. Any institution operating at or near those levels would be expected by the regulators to have well-diversified risk, including no undue interest rate risk exposures, excellent asset quality, high liquidity, and good earnings and, in general, would have to be considered a strong banking organization. All other organizations and any institutions experiencing or anticipating significant growth are expected to maintain capital ratios at least one to two percent above the minimum levels, and higher capital ratios can be required if warranted by particular circumstances or risk profile.

The various regulatory agencies have adopted substantially similar regulations that define the five capital categories (well capitalized, adequately capitalized, undercapitalized, significantly undercapitalized and critically undercapitalized) for classifying insured depository institutions, using the total risk-based capital, Tier 1 risk-based capital and leverage capital ratios as the relevant capital measures, and requires the respective federal regulatory agencies to implement systems for “prompt corrective action” for insured depository institutions that

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do not meet minimum capital requirements within such categories. Such regulations establish progressively more restrictive constraints on operations, management and capital distributions depending on the category in which an institution is classified.

To be “well capitalized” under federal bank regulatory agency definitions, a depository institution must have (i) a Tier 1 risk-based capital ratio of 6% or greater, (ii) a total risk-based capital ratio of 10% or greater, and (iii) a leverage ratio of 5% or greater. An “adequately capitalized” bank is defined as one that has (i) a Tier 1 risk-based capital ratio of 4% or greater, (ii) a total risk-based capital ratio of 8% or greater, and (iii) a leverage ratio of 4% or greater, and an “undercapitalized” bank is defined as one that has (i) a Tier 1 risk-based capital ratio of less than 4%, (ii) a total risk-based capital ratio of less than 8%, and (iii) a leverage ratio of less than 4%. A bank is considered “significantly undercapitalized” if the bank has (i) a Tier 1 risk-based capital ratio of less than 3%, (ii) a total risk-based capital ratio of less than 6%, and (iii) a leverage ratio of less than 3%, and “critically undercapitalized” if the bank has a ratio of tangible equity to total assets equal to or less than 2%. The applicable federal regulatory agency for a bank that is “well capitalized” may reclassify it as an “adequately capitalized” or “undercapitalized” institution and subject it to the supervisory actions applicable to the next lower capital category, if it determines that the Bank is in an unsafe or unsound condition or deems the bank to be engaged in an unsafe or unsound practice and not to have corrected the deficiency. Under Federal banking laws, failure to meet the minimum regulatory capital requirements could subject a banking institution to a variety of enforcement remedies available to federal regulatory authorities, including the termination of deposit insurance by the FDIC and seizure of the institution. As of December 31, 2005, the Bank had a Tier 1 ratio of 10.61%, a combined Tier 1 and Tier 2 ratio of 11.71%, and a leverage ratio of 8.61% and, accordingly, was considered to be “well capitalized” as of such date.

In addition, the Federal Reserve Board has established minimum risk based capital guidelines and leverage ratio guidelines for bank holding companies that are substantially similar to those adopted by bank regulatory agencies with respect to depository institutions. These guidelines provide for a minimum leverage ratio of 3% for bank holding companies that meet certain specified criteria, including those having the highest regulatory rating. All other bank holding companies generally are required to maintain a leverage ratio of at least 4%. As of December 31, 2005, the Company had a Tier 1 ratio of 12.56%, a combined Tier 1 and Tier 2 ratio of 13.65%, and a leverage ratio of 10.08% and, accordingly, was in compliance with all of the Federal Reserve Board’s capital guidelines.

FDICIA and Related Regulations

Prompt Corrective Action

FDICIA provides the Federal banking agencies with broad powers to take “prompt corrective action” to resolve problems of insured depository institutions, depending upon a particular institution’s level of capital, as described above. “Undercapitalized” depository institutions, among other things, are subject to growth limitations, are prohibited, with certain exceptions, from making capital distributions, are limited in their ability to obtain funding from a Federal Reserve Bank and are required to submit a capital restoration plan. The federal banking agencies may not accept a capital plan without determining, among other things, that the plan is based on realistic assumptions and is likely to succeed in restoring the depository institution’s capital. In addition, for a capital restoration plan to be acceptable, the depository institution’s parent holding company must guarantee that the institution will comply with such capital restoration plan and provide appropriate assurances of performance. If a depository institution fails to submit an acceptable plan, including if the holding company refuses or is unable to make the guarantee described in the previous sentence, it is treated as if it is “significantly undercapitalized”. Failure to submit or implement an acceptable capital plan also is grounds for the appointment of a conservator or a receiver. “Significantly undercapitalized” depository institutions may be subject to a number of additional requirements or restrictions, including the requirement to issue additional voting stock to become adequately capitalized and requirements to reduce total assets and cessation of receipt of deposits from correspondent banks. “Critically undercapitalized” institutions, among other things, are prohibited from making any payments of principal and interest on subordinated debt, and are subject to the appointment of a receiver or conservator.

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Under FDICIA, the FDIC is permitted to provide financial assistance to an insured bank before appointment of a conservator or receiver only if (i) such assistance would be the least costly method of meeting the FDIC’s insurance obligations, (ii) grounds for appointment of a conservator or a receiver exist or are likely to exist, (iii) it is unlikely that the bank can meet all capital standards without assistance and (iv) the bank’s management has been competent, has complied with applicable laws, regulations, rules and supervisory directives and has not engaged in any insider dealing, speculative practice or other abusive activity.

Safety and Soundness Standards

FDICIA, as amended, directs each Federal banking agency to prescribe safety and soundness standards for depository institutions relating to internal controls, information systems, internal audit systems, loan documentation, credit underwriting, interest rate exposure, asset growth, compensation, asset-quality, earnings and stock valuation. The Community Development and Regulatory Improvement Act of 1994 amended the FDICIA by allowing Federal banking activities to publish guidelines rather than regulations concerning safety and soundness.

Consumer Protection Provisions

FDICIA also includes provisions requiring advance notice to regulators and customers for any proposed branch closing and authorizing (subject to future appropriation of the necessary funds) reduced insurance assessments for institutions offering “lifeline” banking accounts or engaged in lending in distressed communities. FDICIA also includes provisions requiring depository institutions to make additional and uniform disclosures to depositors with respect to the rates of interest, fees and other terms applicable to consumer deposit accounts.

Regulatory Restrictions on Dividends

BancFirst, as a nonmember state bank, may not declare a dividend without the approval of the FDIC unless the dividend to be declared by BancFirst does not exceed the total of (i) BancFirst’s net profits (as defined and interpreted by regulation) for the current year to date plus (ii) its retained net profits (as defined and interpreted by regulation) for the preceding two years, less any required transfers to surplus. In addition, BancFirst can only pay dividends to the extent that its retained net profits (including the portion transferred to surplus) exceed its bad debts (as defined by regulation). Under the Federal Deposit Insurance Act, no dividends may be paid by an insured bank if the bank is in arrears in the payment of any insurance assessment due to the FDIC. Additionally, state and federal regulatory authorities have adopted standards for the maintenance of adequate levels of capital by banks. See “—Capital Adequacy Guidelines,” above. Adherence to such standards further limits the ability of banks to pay dividends. The payment of dividends by any subsidiary bank may also be affected by other regulatory requirements and policies, such as the maintenance of adequate capital. If, in the opinion of the applicable regulatory authority, a bank under its jurisdiction is engaged in, or is about to engage in, an unsafe or unsound practice (which, depending on the financial condition of the bank, could include the payment of dividends), such authority may require, after notice and hearing, that such bank cease and desist from such practice. The FDIC has formal and informal policies which provide that insured banks should generally pay dividends only out of current operating earnings.

Deposit Insurance and Assessments

BancFirst is insured by the FDIC and is required to pay certain fees and premiums to the Bank Insurance Fund (“BIF”). These deposit insurance premiums are assessed through a risk-based system under which all insured depository institutions are placed into one of nine categories and assessed insurance premiums on deposits based upon their level of capital and supervisory evaluation, with the well-capitalized banks with the highest supervisory rating paying lower or no premiums and the critically undercapitalized banks paying up to 0.27% of deposits. BancFirst is currently not assessed a deposit premium as it is well-capitalized.

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Under the Deposit Insurance Funds Act of 1996 (the “Funds Act”), beginning in 1997 banks insured under the BIF were required to pay a part of the interest on bonds issued by the Financing Corporation (“FICO”) in the late 1980s to recapitalize the defunct Federal Savings and Loan Insurance Corporation. Before the Funds Act, FICO payments were made only by depository institutions that were members of the Savings Association Insurance Fund (the “SAIF”). Under the Funds Act, until January 1, 2000, BIF members were assessed for FICO payments at only one-fifth the rate of assessment on SAIF members. The Funds Act required that, as of January 1, 2000, all BIF- and SAIF- insured institutions pay FICO assessments at the same rate. For the first quarter of 2006, FICO rates have been set at 0.0132% for both BIF and SAIF members. The FICO assessment rates for both BIF and SAIF members for 2005 were:

State Regulation

BancFirst is an Oklahoma-chartered state bank. Accordingly, BancFirst’s operations are subject to various requirements and restrictions of Oklahoma state law relating to loans, lending limits, interest rates payable on deposits, investments, mergers and acquisitions, borrowings, dividends, capital adequacy, and other matters. However, Oklahoma banking law specifically empowers a state-chartered bank such as BancFirst to exercise the same powers as are conferred upon national banks by the laws of the United States and the regulations and policies of the United States Comptroller of the Currency, unless otherwise prohibited or limited by the State Banking Commissioner or the State Banking Board. Accordingly, unless a specific provision of Oklahoma law otherwise provides, a state-chartered bank is empowered to conduct all activities that a national bank may conduct.

National banks are authorized by the Gramm-Leach-Bliley Act to engage, through “financial subsidiaries,” in any activity that is permissible for a financial holding company and any activity that the Secretary of the Treasury, in consultation with the Federal Reserve Board, determines is financial in nature or incidental to any such financial activity, except (1) insurance underwriting, (2) real estate development or real estate investment activities (unless otherwise permitted by law), (3) insurance company portfolio investments and (4) merchant banking. The authority of a national bank to invest in a financial subsidiary is subject to a number of conditions, including, among other things, requirements that the bank must be well managed and well capitalized (after deducting from the bank’s capital outstanding investments in financial subsidiaries). The Gramm-Leach-Bliley Act provides that state nonmember banks, such as the Bank, may invest in financial subsidiaries (assuming they have the requisite investment authority under applicable state law) subject to the same conditions that apply to national bank investments in financial subsidiaries.

Prior to August 2003, BancFirst was a member bank of the Federal Reserve System and subject to dual regulation by the State Banking Board and the Federal Reserve Board. In August 2003, BancFirst elected to no longer be a member bank in the Federal Reserve System and, accordingly, is no longer subject to direct regulation by the Federal Reserve Board. As a state nonmember bank, BancFirst is subject to primary supervision, periodic examination and regulation by the State Banking Board and the FDIC, and Oklahoma law provides that BancFirst must maintain reserves against deposits as required by the Federal Deposit Insurance Act. The Oklahoma State Bank Commissioner is authorized by statute to accept an FDIC examination in lieu of a state examination. In practice, the FDIC and the Oklahoma State Banking Department alternate examinations of BancFirst. If, as a result of an examination of a bank, the Oklahoma Banking Department determines that the financial condition, capital resources, asset quality, earnings prospects, management, liquidity, or other aspects of the bank’s operations are unsatisfactory or that the management of the bank is violating or has violated any law or regulation, various remedies, including the remedy of injunction, are available to the Oklahoma Banking

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Department. Oklahoma law permits the acquisition of an unlimited number of wholly-owned bank subsidiaries so long as aggregate deposits at the time of acquisition in a multi-bank holding company do not exceed 20% of the total amount of deposits of insured depository institutions located in Oklahoma.

In addition to the provisions of the Gramm-Leach-Bliley Act that authorize a state nonmember banks to invest in financial subsidiaries (assuming they have the requisite investment authority under applicable state law) on the same conditions that apply to national banks, FDICIA provides that FDIC-insured state banks such as the Bank may engage directly or through a subsidiary in certain activities that are not permissible for a national bank, if the activity is authorized by applicable state law, the FDIC determines that the activity does not pose a significant risk to the BIF, and the bank is in compliance with its applicable capital standards.

Governmental Monetary and Fiscal Policies

The commercial banking business is affected directly by the monetary policies of the Federal Reserve Board and by the fiscal policies of federal, state and local governments. The Federal Reserve Board, in fulfilling its role of stabilizing the nation’s money supply, utilizes several operating tools, all of which directly impact commercial bank operations. The primary tools used by the Federal Reserve Board are changes in reserve requirements on member bank deposits and other borrowings, open market operations in the U.S. Government securities market, and control over the availability and cost of members’ direct borrowings from the “discount window.” Banks act as financial intermediaries in the debt capital markets and are active participants in these markets daily. As a result, changes in governmental monetary and fiscal policies have a direct impact upon the level of loans and investments, the availability of sources of lendable funds, and the interest rates earned from and paid on these instruments. It is not possible to predict accurately the future course of such government policies and the residual impact upon the operations of the Company.

Other Legislation

Community Reinvestment Act

Under the Community Reinvestment Act, the Bank has a continuing and affirmative obligation consistent with safe and sound banking practices to help meet the needs of its entire community, including low- and moderate-income neighborhoods served by the Bank. The Community Reinvestment Act does not establish specific lending requirements or programs for financial institutions nor does it limit the Bank’s discretion to develop the types of products and services that it believes are best suited to its particular community. On a periodic basis, the FDIC is charged with preparing a written evaluation of the Bank’s record of meeting the credit needs of the entire community and assigning a rating. The bank regulatory agencies will take that record into account in their evaluation of any application made by the Bank or the Company for, among other things, approval of the acquisition or establishment of a branch or other deposit facility, an office relocation, a merger or the acquisition of shares of capital stock of another financial institution. An “unsatisfactory” Community Reinvestment Act rating may be used as the basis to deny an application. In addition, as discussed above, a bank holding company may not become a financial holding company unless each of its subsidiary banks has a Community Reinvestment Act rating of at least “satisfactory”. The Bank was last examined for compliance with the Community Reinvestment Act in 2005, and received a rating of “satisfactory.”

Privacy Provisions of Gramm-Leach-Bliley Act

Under the Gramm-Leach-Bliley Act, federal banking regulators adopted rules that limit the ability of banks and other financial institutions to disclose non-public information about consumers to non-affiliated third parties. These limitations require disclosure of privacy policies to consumers and, in some circumstances, allow consumers to prevent disclosure of certain personal information to non-affiliated third parties. The privacy provisions of the Gramm-Leach-Bliley Act affect how consumer information is transmitted through diversified financial companies and conveyed to outside vendors.

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Other Consumer Protection Laws and Regulations

In addition to the other laws and regulations discussed herein, the Bank is subject to certain consumer and public interest laws and regulations that are designed to protect customers in transactions with banks. While this list is not exhaustive, these laws and regulations include the Truth in Lending Act, the Truth in Savings Act, the Electronic Funds Transfer Act, the Expedited Funds Availability Act, the Equal Credit Opportunity Act, the Fair Housing Act, the Real Estate Settlement Procedures Act, the Home Mortgage Disclosure Act, the Fair Credit Reporting Act, the Fair Debt Collection Practices Act and the Right to Financial Privacy Act. These laws and regulations mandate certain disclosure requirements and regulate the manner in which financial institutions must deal with customers when taking deposits, making loans, collecting loans and providing other services. Failure to comply with these laws and regulations can subject the bank to various penalties, including enforcement actions, injunctions, fines or criminal penalties, punitive damages to consumers and the loss of certain contractual rights.

USA Patriot Act of 2001

In October 2001, the USA Patriot Act of 2001 (the “Patriot Act”) was enacted to amend the Bank Secrecy Act (BSA) and the rules and regulations of the Office of Foreign Assets Control (OFAC) in response to the terrorist attacks in New York, Pennsylvania and Washington, D.C., which occurred on September 11, 2001. Intended to strengthen U.S. law enforcement’s and the intelligence communities’ abilities to work cohesively to combat terrorism on a variety of fronts, the Patriot Act substantially broadened the scope of the U.S. anti-money laundering laws and regulations by imposing significant new compliance and due diligence obligations, creating new crimes and penalties and expanding the extra-territorial jurisdiction of the United States. The U.S. Treasury Department has issued a number of implementing regulations which apply various requirements of the Patriot Act to financial institutions such as the Bank. Those regulations impose new obligations on financial institutions to maintain appropriate policies, procedures and controls to detect, prevent and report money laundering and terrorist financing.

Failure of a financial institution to comply with the Patriot Act’s requirements could have serious legal and reputational consequences for the institution. The Company has adopted appropriate policies, procedures and controls to address compliance with the requirements of the Patriot Act under the existing regulations and will continue to revise and update its policies, procedures and controls to reflect changes required by the Act and its implementing regulations.

Sections 23A and 23B of the Federal Reserve Act and Regulation W

Transactions between a bank and its “affiliates” are governed by Sections 23A and 23B of the Federal Reserve Act, which are intended to protect insured depository institutions from suffering losses arising from transactions with affiliates. An affiliate of a bank is any company or entity that controls, is controlled by or is under common control with the bank. A subsidiary of a bank that is not also a depository institution is not treated as an affiliate of a bank for purposes of Sections 23A and 23B unless it engages in activities not permissible for a national bank to engage in directly. Generally, Sections 23A and 23B (i) limit the extent to which a bank or its subsidiaries may engage in “covered transactions” with any one affiliate to an amount equal to 10% of such institution’s capital stock and surplus, and limit such transactions with all affiliates to an amount equal to 20% of such capital stock and surplus, and (ii) require that all such transactions be on terms that are consistent with safe and sound banking practices. The term “covered transaction” includes the making of loans to an affiliate, the purchase of or investment in securities issued by an affiliate, the purchase of assets from an affiliate, the issuance of a guarantee for the benefit of an affiliate, and similar transactions. Most loans by a bank to any of its affiliates must be secured by collateral in amounts ranging from 100% to 130% of the loan amount, depending on the nature of the collateral. In addition, any covered transaction by a bank with an affiliate and any sale of assets or provision of services to an affiliate must be on terms that are substantially the same, or at least as favorable, to the bank as those prevailing at the time for comparable transactions with nonaffiliated companies. The Bank is also restricted in the loans that it may make to its executive officers, and directors, the executive officers and

directors of the Company, any owner of 10% or more of its stock or the stock of the Company, and certain entities affiliated with any such person.

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On October 31, 2002, the Federal Reserve Board issued a new regulation, Regulation W, that was effective April 1, 2003, which comprehensively implements sections 23A and 23B of the Federal Reserve Act. The regulation unifies and updates staff interpretations issued over the years, incorporates several new interpretative proposals (such as to clarify when transactions with an unrelated third party will be attributed to an affiliate) and addresses new issues arising as a result of the expanded scope of nonbanking activities engaged in by bank and bank holding companies in recent years and authorized for financial holding companies under the Gramm-Leach-Bliley Act.

Sarbanes-Oxley Act of 2002

The Sarbanes-Oxley Act of 2002 (the “SOA”) contains important new requirements for public companies in the area of financial disclosure and corporate governance. In accordance with Section 302(a) of Sarbanes-Oxley, written certifications by the Company’s chief executive officer and chief financial officer are required to be filed with the Company’s quarterly and annual reports. These certifications attest that the Company’s quarterly and annual reports do not contain any untrue statement of a material fact. The Company has also implemented a program designed to comply with Section 404 of Sarbanes-Oxley, which includes the identification of significant processes and accounts, documentation of the design of control effectiveness over processes and entity level controls, and testing of the operating effectiveness of key controls. Although the Company has incurred additional expense in complying with the internal control provisions of the SOA, such compliance has not had a material impact on the Company’s results of operations or financial condition.

Additional provisions of the SOA prohibit a public company’s executives from insider trading during retirement plan “blackout” periods, and restrict loans to company executives (other than loans by financial institutions permitted by federal rules and regulations). The legislation accelerates the time frame for disclosures by public companies, as they must immediately disclose any material changes in their financial condition or operations. Directors and executive officers must also provide information for most changes in beneficial ownership in a company’s securities within two business days of the change. Under the act, longer prison terms apply to corporate executives who violate federal securities laws; the period during which certain types of suits can be brought against a company or its officers is extended; and bonuses issued to top executives prior to restating a company’s financial statements are now subject to disgorgement if such restatement was due to corporate misconduct.

The SOA also increases the oversight of, and codifies certain requirements relating to, audit committees of public companies and how they interact with the company’s “independent registered public accounting firm.” Audit Committee members must be independent and are absolutely barred from accepting consulting, advisory or other compensatory fees from the public company. In addition, companies must disclose whether at least one member of the committee is an “audit committee financial expert” (as defined by SEC regulations) and if not, why not. Under the SOA, a company’s registered public accounting firm will be prohibited from performing statutorily mandated audit services for a company if such company’s chief executive officer, chief financial officer, comptroller, chief accounting officer or any person serving in equivalent positions had been employed by such firm and participated in the audit of such company during the one-year period preceding the audit initiation date. The SOA prohibits any officer or director of a company or any other person acting under their direction from taking any action to fraudulently influence, coerce, manipulate or mislead any independent accountant engaged in the audit of the company’s financial statements for the purpose of rendering the financial statements materially misleading.

Enforcement Authority

The federal banking laws also contain civil and criminal penalties available for use by the appropriate regulatory agency against certain “institution-affiliated parties” primarily including management, employees, and agents of a financial institution, as well as independent contractors such as attorneys, accountants, and others who participate in the conduct of the financial institution’s affairs and who caused or are likely to cause more

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than minimum financial loss to or a significant adverse affect on the institution, who knowingly or recklessly violate a law or regulation, breach a fiduciary duty, or engage in unsafe or unsound practices. These practices can include the failure of an institution to timely file required reports or the submission of inaccurate reports. These laws authorize the appropriate banking agency to issue cease and desist orders that may, among other things, require affirmative action to correct any harm resulting from a violation or practice, including restitution, reimbursement, indemnification, or guarantees against loss. A financial institution may also be ordered to restrict its growth, dispose of certain assets, or take other action as determined by the ordering agency to be appropriate.

Recent Regulatory Developments

On February 8, 2006, President Bush signed the Federal Deposit Insurance Reform Act of 2005 (“FDIRA”) into law as part of the Deficit Reduction Act of 2005 and on February 15, 2006, President Bush signed into law the technical and conforming amendments designed to implement FDIRA. FDIRA provides for legislative reforms to modernize the federal deposit insurance system.

Among other things, FDIRA: (i) merges the BIF and the SAIF of the FDIC into a new Deposit Insurance Fund (the “DIF”); (ii) allows the FDIC, after March 31, 2010, to increase deposit insurance coverage by an adjustment for inflation and requires the FDIC’s Board of Directors, not later than April 1, 2010 and every five years thereafter, to consider whether such an increase is warranted; (iii) increases the deposit insurance limit for certain employee benefit plan deposits from $100,000 to $250,000, subject to adjustments for inflation after March 31, 2010, and provides for pass-through insurance coverage for such deposits; (iv) increases the deposit insurance limit for certain retirement account deposits from $100,000 to $250,000, subject to adjustments for inflation after March 31, 2010; (v) allows the FDIC’s Board of Directors to set deposit insurance premium assessments in any amount the Board of Directors deems necessary or appropriate, after taking into account various factors specified in FDIRA; (vi) replaces the fixed designated reserve ratio of 1.25% with a reserve ratio range of 1.15%-1.50%, with the specific reserve ratio to be determined annually by the FDIC by regulation; (vii) permits the FDIC to revise the risk-based assessment system by regulation; (viii) requires the FDIC, at the end of any year in which the reserve ratio of the DIF exceeds 1.5% of estimated insured deposits, to declare a dividend payable to insured depository institutions in an amount equal to 100% of the amount held by the DIF in excess of the amount necessary to maintain the DIF’s reserve ratio at 1.5% of estimated insured deposits or to declare a dividend equal to 50% of the amount in excess of the amount necessary to maintain the reserve ratio at 1.35% if the reserve ratio is between 1.35%-1.5% of estimated insured deposits; and (ix) provides a one-time credit based upon the assessment base of the institution on December 31, 1996 to each insured depository institution that was in existence as of December 31, 1996 and paid a deposit insurance assessment prior to that date (or a successor to any such institution).

The merger of the BIF and SAIF takes effect July 1, 2006, while the remaining provisions are not effective until the FDIC issues final regulations. FDIRA requires the FDIC to issue final regulations no later than 270 days after enactment: (i) designating a reserve ratio; (ii) implementing increases in deposit insurance coverage; (iii) implementing the dividend requirement; (iv) implementing the one-time assessment credit; and (v) providing for assessments in accordance with FDIRA.

Pending and Proposed Legislation

There are various pending and proposed bills in Congress that, among other things, could restructure the federal supervision of financial institutions. The Company is unable to predict with any certainty the effect any such legislation would have on the Company, its subsidiaries or their respective activities. Additional legislation, judicial and administrative decisions also may affect the ability of banks to compete with each other as well as with other businesses. These statutes and decisions may tend to make the operations of various financial institutions more similar and increase competition among banks and other financial institutions or limit the ability of banks to compete with other businesses. Management currently cannot predict whether and, if so, when any such changes might occur or the impact any such changes would have upon the income or operations of the Company or its subsidiaries, or upon the Oklahoma regional banking environment.

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Item 1a. Risk Factors

An investment in our common stock involves risks. Investors should carefully consider the risks described below in conjunction with the other information in this report, including our consolidated financial statements with related notes and documents incorporated by reference. If any of the following risks or other risks, which have not been identified or which we may believe are immaterial or unlikely, actually occur, our business, financial condition and results of operations could be harmed. In such case, the trading price of our common stock could decline, and investors may lose all or part of their investment.

Risks Related to Our Business

Our recent results may not be indicative of future results.

We may not be able to sustain our historical rate of growth or may not be able to grow our business at all. Various factors, such as poor economic conditions, changes in interest rates, regulatory and legislative considerations and competition may also impede or inhibit our ability to expand our market presence. If we experience a significant decrease in our rate of growth, our results of operations and financial condition may be adversely affected due to a high percentage of our operating costs being fixed expenses.

Our directors and executive officers own a significant portion of our common stock and can influence shareholder decisions.

Our directors and executive officers, as a group, beneficially owned approximately 53% of the Company’s outstanding common stock as of February 28, 2006. As a result of their ownership, the directors and executive officers have the ability, by voting their shares in concert, to influence the outcome of any matter submitted to our shareholders for approval, including the election of directors. The directors and executive officers may vote to cause the Company to take actions with which our other shareholders do not agree.

Adverse changes in economic conditions, especially in the State of Oklahoma, could have a material adverse effect on our business, growth, and profitability.

Our bank subsidiary operates exclusively within the State of Oklahoma, and as a result, our financial condition, results of operations and cash flows are subject to changes in the economic conditions in such state. Our continued success is largely dependent upon the continued growth of the communities we serve. A decline in the growth of these communities could negatively impact our net income and profitability. Additionally, declines in the economies of these communities and of the State of Oklahoma in general could affect our ability to generate new loans or to receive repayments of existing loans, adversely affecting our financial condition.

Competition with other financial institutions could adversely affect our profitability.

We face vigorous competition from banks and other financial institutions, including savings and loan associations, savings banks, finance companies and credit unions. A number of these banks and other financial institutions have substantially greater resources and lending limits, larger branch systems and a wider array of banking services. To a limited extent, we also compete with other providers of financial services, such as money market mutual funds, brokerage firms, consumer finance companies and insurance companies. When new competitors seek to enter one of our markets, or when existing market participants seek to increase their market share, they sometimes undercut the pricing and/or credit terms prevalent in that market. This competition may reduce or limit our margins on banking and trust services, reduce our market share and adversely affect our results of operations and financial condition. If Regulation Q is repealed and financial institutions are allowed to pay interest on demand deposits, competitive pressures might cause the Company’s subsidiary bank to pay interest on demand deposits. Since the Company has a higher than average level of demand deposits, paying interest on demand deposits would have a negative impact on the Company’s net interest margin.

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The Company’s concentration of real estate loans is subject to the local real estate market in which it operates.

Loans secured by real estate have been a large portion of the Company’s loan portfolio. In 2005, this percentage was 60.0%. The Company is subject to risk of future market fluctuations in property values relating to these loans. The Company attempts to manage this risk through rigorous loan underwriting standards, training of loan officers and close monitoring of the valuation of individual properties collateralizing the loan.

We rely heavily on our management team, and the unexpected loss of key managers may adversely affect our operations.

Our success to date has been strongly influenced by our ability to attract and to retain senior management experienced in banking and financial services. Our ability to retain executive officers and the current management teams of each of our lines of business will continue to be important to successful implementation of our strategies. We do not have employment or non-compete agreements with these key employees. The unexpected loss of services of any key management personnel, or the inability to recruit and retain qualified personnel in the future, could have an adverse effect on our business and financial results.

There can be no assurance that the integration of our acquisitions will be successful or will not result in unforeseen difficulties that may absorb significant management attention.

Our completed acquisitions, or any future acquisition, may not produce the revenue, earnings or synergies that we anticipated. The process of integrating acquired companies into our business may also result in unforeseen difficulties. Unforeseen operating difficulties may absorb significant management attention, which we might otherwise devote to our existing business. Also, the process may require significant financial resources that we might otherwise allocate to other activities, including the ongoing development or expansion of our existing operations.

If we pursue a future acquisition, our management could spend a significant amount of time and effort identifying and completing the acquisition. If we make a future acquisition, we could issue equity securities which would dilute current stockholders’ percentage ownership, incur substantial debt, assume contingent liabilities, incur a one-time charge or be required to record an impairment of goodwill, or any combination of the foregoing.

If we fail to maintain an effective system of internal controls, we may not be able to accurately report our financial results or prevent fraud.

Effective internal controls are necessary for us to provide reliable financial reports and effectively prevent fraud. Any inability to provide reliable financial reports or prevent fraud could harm our business. The Sarbanes-Oxley Act of 2002 requires management and our auditors to evaluate and assess the effectiveness of our internal controls. These Sarbanes-Oxley requirements may be modified, supplemented or amended from time to time. Implementing these changes may take a significant amount of time and may require specific compliance training of our personnel. We have in the past discovered, and may in the future discover, areas of our internal controls that need improvement. If we or our auditors discover a material weakness, the disclosure of that fact, even if quickly remedied, could reduce the market’s confidence in our financial statements and harm our stock price. We may not be able to effectively and timely implement necessary control changes and employee training to ensure continued compliance with the Sarbanes-Oxley Act and other regulatory and reporting requirements. Our historic growth and our planned expansion through acquisitions present challenges to maintain the internal control and disclosure control standards applicable to public companies. If we fail to maintain effective internal controls we could be subject to regulatory scrutiny and sanctions, our ability to recognize revenue could be impaired and investors could lose confidence in the accuracy and completeness of our financial reports. We cannot assure you that we will be able to fully comply with the requirements of the Sarbanes-Oxley Act or that management or our auditors will conclude that our internal controls are effective in future periods.

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Maintaining or increasing our market share depends on market acceptance and regulatory approval of new products and services

Our success depends, in part, upon our ability to adapt our products and services to evolving industry standards and consumer demand. There is increasing pressure on financial services companies to provide products and services at lower prices. In addition, the widespread adoption of new technologies, including Internet-based services, could require us to make substantial expenditures to modify or adapt our existing products or services. A failure to achieve market acceptance of any new products we introduce, or a failure to introduce products that the market may demand, could have an adverse effect on our business, profitability, or growth prospects.

We have businesses other than banking.

In addition to commercial banking services, we provide life and other insurance products, as well as other business and financial services. We may in the future develop or acquire other non-banking businesses. As a result of other such businesses, our earnings could be subject to risks and uncertainties that are different from those to which our commercial banking services are subject.

We have a continuing need for technological change.

The financial services industry is undergoing rapid technological changes with frequent introductions of new technology-driven products and services. In addition to better serving customers, the effective use of technology increases efficiency and enables financial institutions to reduce costs. Our future success will depend in part upon our ability to address the needs of our customers by using technology to provide products and services that will satisfy customer demands for convenience as well as to create additional efficiencies in our operations as we continue to grow and expand our market area. Many of our larger competitors have substantially greater resources to invest in technological improvements. As a result, they may be able to offer additional or superior products to those that we will be able to offer, which would put us at a competitive disadvantage. Accordingly, we cannot assure you that we will be able to effectively implement new technology-driven products and services or be successful in marketing such products and services to our customers.

Our stockholder rights plan, amended and restated certificate of incorporation, as well as provisions of Oklahoma law, could make it difficult for a third party to acquire our company.

We have a stockholder rights plan that may have the effect of discouraging unsolicited takeover proposals. The rights issued under the stockholder rights plan would cause substantial dilution to a person or group that attempts to acquire us on terms not approved in advance by our board of directors. In addition, Oklahoma corporate law and our amended and restated certificate of incorporation contain provisions that could delay, deter or prevent a change in control of our company or our management. Together, these provisions may discourage transactions that otherwise could provide for the payment of a premium over prevailing market prices of our common stock, and also could limit the price that investors are willing to pay in the future for shares of our common stock.

Risks Related to Our Industry

Fluctuations in interest rates could reduce our profitability.

We realize income primarily from the difference between interest earned on loans and investments and the interest paid on deposits and borrowings. We expect that we will periodically experience “gaps” in the interest rate sensitivities of our assets and liabilities, meaning that either our interest-earning assets will be more sensitive to changes in market interest rates than our interest-bearing liabilities, or vice versa. Changes in market interest rates could either positively or negatively affect our net interest income and our profitability, depending on the magnitude, direction and duration of the change.

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We are unable to predict fluctuations of market interest rates, which are affected by, among other factors, changes in inflation rates, economic growth, money supply, government debt, domestic and foreign financial markets and political developments, including terrorist acts and acts of war. Our asset-liability management strategy, which is designed to mitigate our risk from changes in market interest rates, may not be able to mitigate changes in interest rates from having a material adverse effect on our results of operations and financial condition.

If a significant number of customers fail to perform under their loans, our business, profitability, and financial condition would be adversely affected.

As a lender, we face the risk that a significant number of our borrowers will fail to pay their loans when due. If borrower defaults cause losses in excess of our allowance for loan losses, it could have an adverse effect on our business, profitability, and financial condition. We have established an evaluation process designed to determine the adequacy of the allowance for loan losses. While this evaluation process uses historical and other objective information, the classification of loans and the establishment of loan losses are dependent to a great extent on our experience and judgment. We cannot assure you that our allowance for loan losses will be sufficient to absorb future loan losses or prevent a material adverse effect on our business, profitability or financial condition.

We operate in a highly regulated environment and may be adversely affected by changes in federal and state laws and regulations.

We are subject to extensive regulation, supervision and examination by federal and state banking authorities. Any change in applicable regulations or federal or state legislation could have a substantial impact on us and our results of operations. Additional legislation and regulations may be enacted or adopted in the future that could significantly affect our powers, authority and operations, which could have a material adverse effect on our financial condition and results of operations. Further, regulators have significant discretion and power to prevent or remedy unsafe or unsound practices or violations of laws by banks and bank holding companies in the performance of their supervisory and enforcement duties. The exercise of regulatory power may have a negative impact on our results of operations and financial condition.

Recent changes in laws and regulations may cause us to incur additional costs.

Recently enacted and proposed changes in the laws and regulations affecting public companies, including the provisions of the Sarbanes-Oxley Act of 2002 and rules recently adopted by the Securities and Exchange Commission and Nasdaq Stock Market, Inc., could cause us to incur increased costs as we evaluate the implications of new rules and respond to new requirements. We continue to evaluate and monitor developments with respect to these new and proposed rules, and we cannot predict or estimate the amount of the additional costs, if any, we may incur or the timing of such costs.

Changes in monetary policies may have an adverse effect on our business.

Our results of operations are affected by credit policies of monetary authorities, particularly the Federal Reserve. Actions by monetary and fiscal authorities, including the Federal Reserve, could have an adverse effect on our deposit levels, loan demand or business earnings. See “Business-Supervision and Regulation.”

Item 1b. Unresolved Staff Comments

None.

Item 2. Properties.

The principal offices of the Company are located at 101 North Broadway, Oklahoma City, Oklahoma 73102. The Company owns substantially all of the properties and buildings in which its various offices and facilities are located. These properties include the main bank and 83 branches. BancFirst also owns properties for future expansion. There are no significant encumbrances on any of these properties.

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Item 3. Legal Proceedings.

The Company has been named as a defendant in various legal actions arising from the conduct of its normal business activities. Although the amount of any liability that could arise with respect to these actions cannot be accurately predicted, in the opinion of the Company, any such liability will not have a material adverse effect on the consolidated financial position or results of operations of the Company.

Item 4. Submission of Matters to Vote of Security Holders.

There were no matters submitted to a vote of security holders, through the solicitation of proxies or otherwise, during the fourth quarter of the year ended December 31, 2005.

PART II

Item 5. Market for the Registrant’s Common Equity and Related Stockholder Matters and Issuer Purchases of Equity Securities.

The Company’s Common Stock is listed on the Nasdaq National Market System (“NASDAQ/NMS”) and is traded under the symbol “BANF”. The following table sets forth, for the periods indicated, (i) the high and low sales prices of the Company’s Common Stock (after giving retroactive effect to the registrant’s two-for-one stock split effective March 1, 2006) as reported in the NASDAQ/NMS consolidated transaction reporting system and (ii) the quarterly dividends per share declared on the Common Stock.

As of February 28, 2006 there were approximately 400 holders of record of the Common Stock.

Future dividend payments will be determined by the Company’s Board of Directors in light of the earnings and financial condition of the Company and the Bank, their capital needs, applicable governmental policies and regulations and such other factors as the Board of Directors deems appropriate.

BancFirst Corporation is a legal entity separate and distinct from the Bank, and its ability to pay dividends is substantially dependent upon dividend payments received from the Bank. Various laws, regulations and regulatory policies limit the Bank’s ability to pay dividends to BancFirst Corporation, as well as BancFirst Corporation’s ability to pay dividends to its shareholders. See “Liquidity and Funding” and “Capital Resources” under “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” “Description of Business—Supervision and Regulation” and note 14 of the Notes to Consolidated Financial Statements for further information regarding limitations on the payment of dividends by BancFirst Corporation and the Bank.

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Item 6. Selected Financial Data.

Incorporated by reference from “Selected Consolidated Financial Data” contained on page A-3 of the attached Appendix.

Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations.

Incorporated by reference from “Financial Review” contained on pages A-2 through A-19 of the attached Appendix.

Item 7A. Quantitative and Qualitative Disclosures About Market Risk.

Incorporated by reference from “Financial Review—Market Risk” contained on page A-16 through A-17 of the attached Appendix.

Item 8. Financial Statements and Supplementary Data.

The consolidated financial statements of BancFirst Corporation and its subsidiaries, are incorporated by reference from pages A-21 through A-55 of the attached Appendix, and include the following:

Item 9. Changes in and Disagreements with Accountants on Accounting and Financial Disclosure.

On May 26, 2005, the Company’s audit committee elected to dismiss Ernst & Young LLP as its independent registered public accounting firm effective May 31, 2005. In connection with its audits for the two most recent fiscal years and through May 31, 2005, there were no disagreements with Ernst & Young LLP on any matter of accounting principles or practices, financial statement disclosure, or auditing scope or procedure, which disagreements if not resolved to the satisfaction of Ernst & Young LLP would have caused them to make reference thereto in their reports on the financial statements for such years.

Effective on June 7, 2005, the Company engaged Grant Thornton LLP as its new independent registered public accounting firm. Prior to its appointment as independent registered public accounting firm, Grant Thornton LLP has not been consulted by the Company on any of the matters referenced in Regulation S-K Item 304 (a) (2).

Item 9A. Controls and Procedures.

The Company’s Chief Executive Officer, Chief Financial Officer and Disclosure Committee, which includes the Company’s Chief Risk Officer, Chief Asset Quality Officer, Chief Internal Auditor, Senior Vice President of Corporate Finance, Holding Company Controller, Bank Controller and General Counsel, have evaluated, as of the last day of the period covered by this report, the Company’s disclosure controls and procedures. Based on their evaluation they concluded that the disclosure controls and procedures of the Company are adequate to ensure that information required to be disclosed by the Company in the reports filed or submitted by it under the Securities Exchange Act of 1934 is recorded, processed, summarized and reported, within the time periods specified in the applicable rules and forms. There have been no significant changes in the Company’s internal controls or in other factors that could significantly affect internal controls subsequent to the date of their evaluation.

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Management’s annual report on internal control over financial reporting is incorporated by reference from page A-20 of the attached Appendix. The independent registered public accounting firm’s attestation report on management’s assessment of the Company’s internal control over financial reporting is incorporated by reference from page A-20 of the attached Appendix.

Item 9B. Other Information

There is no information required to be disclosed in a report on Form 8-K during the fourth quarter of the year that was not reported.

PART III

Item 10. Directors and Executive Officers of the Registrant.

The information required by Item 401 of Regulation S-K will be contained in the 2006 Proxy Statement under the caption “Election of Directors” and is hereby incorporated by reference. The information required by Item 405 of Regulation S-K will be contained in the 2006 Proxy Statement under the caption “Compliance with Section 16(a) of the Securities Exchange Act of 1934” and is hereby incorporated by reference. The information required by Item 406 of Regulation S-K will be contained in the 2006 Proxy Statement under the caption “Code of Ethics” and is hereby incorporated by reference.

Item 11. Executive Compensation.

The information required by Item 402 of Regulation S-K will be contained in the 2006 Proxy Statement under the caption “Compensation of Directors and Executive Officers” and is hereby incorporated by reference.

Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters.

The information required by Item 201(d) of Regulation S-K will be contained in the 2006 Proxy Statement under the caption “Securities Authorized for Issuance under Equity Compensation Plans” and is hereby incorporated by reference. The information required by Item 403 of Regulation S-K will be contained in the 2006 Proxy Statement under the caption “Security Ownership of Certain Beneficial Owners and Management” and is hereby incorporated by reference.

Item 13. Certain Relationships and Related Transactions.

The information required by Item 404 of Regulation S-K will be contained in the 2006 Proxy Statement under the caption “Transactions with Management” and is hereby incorporated by reference.

Item 14. Principal Accountant Fees and Services.

The information required by Item 9(e) of Schedule 14A will be contained in the 2006 Proxy Statement under the caption “Ratification of Selection of Independent Registered Public Accounting Firm” and is hereby incorporated by reference.

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PART IV

Item 15. Exhibits and Financial Statement Schedules.

(a) The following documents are filed as part of this report:

(1) Financial Statements:

Report of Independent Registered Public Accounting Firm

Consolidated Balance Sheets at December 31, 2005 and 2004

Consolidated Statements of Income and Comprehensive Income for the three years ended December 31, 2005

Consolidated Statements of Stockholders’ Equity for the three years ended December 31, 2005

Consolidated Statements of Cash Flow for the three years ended December 31, 2005

Notes to Consolidated Financial Statements

The above financial statements are incorporated by reference from pages A-21 through A-55 of the attached Appendix.

(2) All other schedules are omitted because they are not applicable or the required information is shown in the financial statements or notes thereto.

(3) The following Exhibits are filed with this Report or are incorporated by reference as set forth below:

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SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Pursuant to the requirements of the Securities Exchange Act of 1934, this report has been signed below by the following persons on behalf of the registrant and in the capacities indicated on March 14, 2006.

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APPENDIX A

BancFirst Corporation

INDEX TO FINANCIAL STATEMENTS

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FINANCIAL REVIEW

The following discussion is an analysis of the financial condition and results of operations of the Company for the three years ended December 31, 2005 and should be read in conjunction with the Consolidated Financial Statements and Notes thereto and the Selected Consolidated Financial Data included herein. All share and per share amounts included in the following consolidated financial data have been retroactively adjusted to reflect our recent two-for-one stock split effective March 1, 2006.

SUMMARY

BancFirst Corporation’s net income for 2005 was $42.8 million, or $2.68 per diluted share, compared to $37.2 million, or $2.33 per diluted share for 2004. The 2005 results include after tax losses totaling $1.95 million on a $3.25 million cash shortfall at one of our branches recorded during 2005. Net interest income increased $14.21 million, or 12.1%, compared to 2004. The increase in net interest income for 2005 resulted from loan growth of $223.9 million which was funded primarily by deposit growth and a reduction in investments. The change in mix of earning assets produced a positive volume variance while increasing rates produced a positive rate variance. Provisions for loan losses in 2005 increased to $4.61 million from $2.70 million for 2004. Noninterest income increased to $54.3 million from $51.9 million, while noninterest expense increased to $117 million from $109 million. The increase in noninterest income is due to an increase in cash management and electronic banking services and sales of insurance products. The increase in noninterest expense in 2005 includes the previously mentioned loss from a $3.25 million cash shortfall. Wilcox & Jones is included in the results of operations beginning upon acquisition in the fourth quarter of 2004 and for the twelve months ended December 31, 2005.

Total assets increased to $3.22 billion from $3.05 billion at the end of 2004. Total loans increased to $2.32 billion from $2.09 billion for 2004. Total deposits increased to $2.80 billion from $2.66 billion for 2004. The Company’s average loans-to-deposits was 82.43% for 2005, compared to 74.47% for 2004. Stockholders’ equity increased to $302 million from $277 million at the end of 2004. Average stockholders’ equity to average assets increased to 9.37% at year-end 2005 from 8.85% at year-end 2004.

Asset quality remained strong in 2005 with nonperforming and restructured assets to total assets decreasing to 0.36% at year-end 2005 from 0.48% at year-end 2004. The allowance for loan losses to nonperforming and restructured loans was 293.36% at December 31, 2005, compared to 211.05% at the end of 2004. Net charge-offs for 2005 were only 0.14% of average loans, compared to 0.16% of average loans for 2004.

The Company has continued to repurchase shares of its common stock under its ongoing Stock Repurchase Program (the “SRP”). During 2005, 130,200 shares were repurchased for consideration of $4.58 million or $35.18 average price per share, compared to 83,000 shares repurchased for $2.36 million or an average of $28.43 per share in 2004. At December 31, 2005, there were 286,052 shares remaining that could be repurchased under the SRP.

In January 2004, the Company established BFC Capital Trust II (“BFC II”), a trust formed under the Delaware Business Trust Act listed on the Nasdaq National Market System (“NASDAQ/NMS”) and is traded under the symbol “BANFP”. The Company owns all of the common securities of BFC II. In February 2004, BFC II issued $25.0 million of aggregate liquidation amount of 7.20% Cumulative Trust Preferred Securities (the “Trust Preferred Securities”) to other investors. In March 2004, BFC II issued an additional $1.0 million in Trust Preferred Securities through the execution of an over-allotment option. The proceeds from the sale of the Trust Preferred Securities and the common securities of BFC II were invested in $26.8 million of 7.20% Junior Subordinated Debentures of BancFirst Corporation. Interest payments on the 7.20% Junior Subordinated Debentures are payable January 15, April 15, July 15 and October 15 of each year. The stated maturity date of the 7.20% Junior Subordinated Debentures is March 31, 2034, but they are subject to mandatory redemption pursuant to optional prepayment terms.

In October 2004, the Company completed the acquisition of Wilcox & Jones, Inc., an independent insurance agency headquartered in Tulsa, Oklahoma for $4.8 million. As a result of the acquisition, Wilcox & Jones became a wholly-owned subsidiary of BancFirst Corporation. The acquisition was accounted for as a purchase.

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Accordingly, the effects of the acquisition have been included in the Company’s consolidated financial statements from the date of the acquisition forward.

In December 2005, BancFirst Corporation completed the acquisition of Park State Bank (Park State), Nicoma Park, Oklahoma for cash of approximately $11 million. Park State had total assets of approximately $44 million. As a result of the acquisition, Park State became a wholly-owned subsidiary of BancFirst Corporation and was merged into BancFirst in February 2006. The acquisition was accounted for as a purchase. Accordingly, the effects of the acquisition are included in the Company’s consolidated financial statements from the date of the acquisition forward. The acquisition did not have a material effect on the results of operations of the Company for 2005.

SELECTED CONSOLIDATED FINANCIAL DATA

(Dollars in thousands, except per share data)

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CONSOLIDATED AVERAGE BALANCE SHEETS AND INTEREST MARGIN ANALYSIS

Taxable Equivalent Basis (Dollars in thousands)

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RESULTS OF OPERATIONS

Net Interest Income

Net interest income, which is the Company’s principal source of operating revenue, increased $14.21 million to $131 million compared to 2004. The net interest margin on a taxable equivalent basis for 2005 was 4.76%, compared to 4.29% for 2004 and 4.27% for 2003. On a taxable equivalent basis, net interest income increased $13.62 million in 2005, compared to $7.66 million in 2004. Changes in the volume of earning assets and interest-bearing liabilities, and changes in interest rates determine the changes in net interest income. The Volume/Rate Analysis summarizes the relative contribution of each of these components to the changes in net interest income in 2005 and 2004. The increase in 2005 was due to loan growth, net of the decrease in other earning assets, that increased interest income by $9.3 million and a favorable rate environment which increased net interest income by $3.7 million. The increase in 2004 was due to loan and investment growth that increased interest income by $11.0 million, which was partially offset by changes in the mix and volume in deposits and volume in junior subordinated debentures that decreased net interest income by $1.03 million and lower interest rates that reduced net interest income by $2.32 million. Average loans grew $228.8 million, or 11.55%, in 2005 and $159.0 million, or 8.72%, in 2004. Average time deposits decreased $34.4 million, or 4.79%, in 2005 and $50.3 million, or 6.55%, in 2004, while average total deposits increased in both years.

VOLUME/RATE ANALYSIS

Taxable Equivalent Basis

Interest rate sensitivity analysis measures the sensitivity of the Company’s net interest margin to changes in interest rates by analyzing the repricing relationship between its earning assets and interest-bearing liabilities. This analysis is limited by the fact that it presents a static position as of a single day and is not necessarily indicative of the Company’s position at any other point in time, and does not take into account the sensitivity of

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yields and rates of specific assets and liabilities to changes in market rates. The Company has continued its strategy of creating manageable negative interest sensitivity gaps in the short term. This approach takes advantage of the Company’s stable core deposit base and the relatively short maturity and repricing frequency of its loan portfolio, as well as the historical existence of a positive yield curve, which enhances the net interest margin over the long term. Although interest rate risk is increased on a controlled basis by this position, it is somewhat mitigated by the Company’s high level of liquidity.

The Analysis of Interest Rate Sensitivity presents the Company’s earning assets and interest-bearing liabilities based on maturity and repricing frequency at December 31, 2005. The Company’s cumulative negative gap position in the one year interval decreased to $499 million at December 31, 2005 from $612 million at December 31, 2004, and decreased as a percentage of total earning assets to 17.34% from 21.86%. This negative gap position assumes that the Company’s core savings and transaction deposits are immediately rate sensitive and reflects management’s perception that the yield curve will be positively sloped over the long term. In the current environment of rising interest rates, the Company’s ability to manage the repricing of its liability rates may enable the Company to improve the net interest margin over time. Additionally, in a rising rate environment, the benefit of the Company’s noninterest-bearing funds is increased, resulting in an increase in the Company’s net interest margin over time.

ANALYSIS OF INTEREST RATE SENSITIVITY

December 31, 2005