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SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark one)

For the fiscal year ended December 31, 2005

For the transition period from                      to                     .

Commission file number 0-25034

GREATER BAY BANCORP

(Exact name of registrant as specified in its charter)

1900 University Avenue, 6^th Floor East Palo Alto, California 94303

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code: (650) 813-8200

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

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

Common Stock, no par value

Guarantee of Greater Bay Bancorp with respect to the

9.00% Cumulative Trust Preferred Securities of GBB Capital V

Preferred Share Purchase Rights

(Title of classes)

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

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 to be filed 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 the 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. (Check one):

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

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

The aggregate market value of the Common Stock held by non-affiliates, based upon the closing sale price of the Common Stock on June 30, 2005, as reported on the Nasdaq National Market System (or “Nasdaq”), was approximately $1,072,881,000. Shares of Common Stock held by each officer, director and holder of 5% or more of the outstanding Common Stock have been excluded in that such persons may be deemed to be affiliates. Such determination of affiliate status is not necessarily a conclusive determination for other purposes.

As of February 28, 2006, 50,146,293 shares of the registrant’s Common Stock were outstanding.

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GREATER BAY BANCORP

ANNUAL REPORT ON FORM 10-K

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GREATER BAY BANCORP

ANNUAL REPORT ON FORM 10-K

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GREATER BAY BANCORP

ANNUAL REPORT ON FORM 10-K

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GREATER BAY BANCORP

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GREATER BAY BANCORP

ANNUAL REPORT ON FORM 10-K

PART I

Discussions of certain matters contained in this Annual Report on Form 10-K may constitute forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities and Exchange Act of 1934, as amended (or “the Exchange Act”) and as such, which involve risks and uncertainties. These forward-looking statements relate to, among other things, expectations of the business environment in which Greater Bay Bancorp and its subsidiaries operate, projections of future performance, and perceived opportunities in the market. Our actual results, performance, and achievements may differ significantly from the results, performance, and achievements expressed or implied in such forward-looking statements. Factors that might cause such a difference include, but are not limited to, economic conditions, competition in the geographic and business areas in which we conduct our operations, fluctuation in interest rates, credit quality, government regulations, and other factors discussed in this Annual Report on Form 10-K for the year ended December 31, 2005. For a discussion of some of the factors that might cause such a difference, see ITEM 1A. “Risk Factors.” Greater Bay Bancorp does not undertake, and specifically disclaims, any obligation to update any forward-looking statements to reflect the occurrence of events or circumstances after the date of such statements.

Greater Bay Bancorp

Greater Bay Bancorp (or on an unconsolidated basis, “the holding company”) is a financial holding company with one bank subsidiary, Greater Bay Bank, National Association (or “the Bank”) and one commercial insurance brokerage subsidiary, ABD Insurance and Financial Services (or “ABD”). The Bank provides community banking services in the greater San Francisco Bay Area through its community banking organization, including Bank of Petaluma, Bank of Santa Clara, Bay Area Bank, Bay Bank of Commerce, Coast Commercial Bank, Cupertino National Bank, Golden Gate Bank, Mid-Peninsula Bank, Mt. Diablo National Bank, Peninsula Bank of Commerce, and San Jose National Bank. Nationally, the Bank provides customized lending services through its specialty finance group, which includes Matsco Companies, Inc. (or “Matsco”), Greater Bay Bank Small Business Administration (or “SBA”) Lending Group, Greater Bay Business Funding, and Greater Bay Capital. ABD provides employee benefits consulting and risk management solutions to business clients throughout the United States.

History

Greater Bay Bancorp (or “we”, “us” or “our” on a consolidated basis) was formed as the result of the November 1996 merger of Cupertino National Bancorp with and into Mid-Peninsula Bancorp. On consummation of the merger, Mid-Peninsula Bancorp changed its name to Greater Bay Bancorp and Cupertino National Bank and Mid-Peninsula Bank became wholly owned subsidiaries of the holding company. Since our formation, we have continued to expand our presence within our market areas by affiliating with other quality banking organizations and select niche financial services companies. From 1997 through 2005, we acquired nine banking institutions, three insurance brokerage firms and three specialty finance companies. In addition, we have been successful in opening key regional banking offices to respond to market and client demands, while also selectively opening key new businesses that expand our product offerings.

On February 1, 2004, we completed the merger of our wholly owned bank subsidiaries into Mid-Peninsula Bank, which was renamed Greater Bay Bank, National Association. The Bank has continued to operate in the same communities and under the same names as before the merger. The merger provides us with the opportunity to streamline our back-office operations, improve the efficiency of our risk management processes, reduce

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corporate governance requirements, and reduce our regulatory reporting burden. During 2005, we completed the systems integration of the 11 back-office systems into a single merged system. This integration did not result in any material changes in our internal control environment or our internal controls over financial reporting or cause any significant client disruption.

Regional Community Banking Philosophy

In order to meet the demands of the increasingly competitive banking and financial services industries, we operate under a “Regional Community Banking Philosophy.” Our Regional Community Banking Philosophy is based on our belief that banking clients value doing business with locally managed banking offices that can provide a full service commercial banking relationship through an understanding of the clients’ financial needs and the flexibility to deliver customized solutions.

Our community banking offices have established strong reputations and client followings in their market areas through our relationship managers’ attention to client service and an understanding of client needs. The primary focus for our relationship managers is to cultivate and nurture their client relationships. Relationship managers are assigned to clients to provide continuity in the relationship. This emphasis on personalized relationships requires relationship managers to maintain close ties to the communities they serve. These community ties help relationship managers expand their business development opportunities.

Our Family of Companies

We provide a wide range of banking and financial services to small and medium-sized businesses, property managers, business executives, real estate developers, professionals, and other individuals. Our lines of business are organized along eight segments, seven of which provide services to our clients, and one that provides services internally to the other segments. The services that these segments provide are as follows:

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Lending Activities

Underwriting and Credit Administration

The Bank’s lending activities are guided by Board approved lending policies, which are recommended by our Credit Policy Committee. Each loan must meet minimum underwriting criteria established in the Bank’s lending policy. Designated credit officers consider loan applications. Larger and more complex transactions are recommended or approved by more experienced senior credit managers who are independent of the lending function. Senior management of the Bank approves lending decisions above Board-designated dollar amounts.

The Bank’s Board of Directors, the Credit Policy Committee, and the Credit Risk Management Committee review a variety of information on a monthly or quarterly basis to monitor the level of credit risk and risk trends within the Bank’s loan portfolio.

The Bank’s Credit Policy Committee includes members of both senior credit management and executive management. It meets monthly to evaluate credit policy and procedures and recommends changes as appropriate to the Board of Directors.

The Bank’s Credit Risk Management Committee, consisting of senior managers from both Credit Administration and line credit units, approves, on a monthly basis, risk rating and specific valuation allowance changes for all large problem loans. In addition, the Credit Risk Management Committee reviews the status of all problem loans. Both the Credit Risk Management Committee and the Board of Directors monitor credit risk measures and trends relating to classified and non-performing assets, charge-offs, delinquencies, and portfolio growth.

On a quarterly basis, the Credit Policy Committee and the Board of Directors review and approve the Bank’s methodology used to establish the allowance for loan and lease losses and the reserve for unfunded credit commitments, and the resulting provision for credit losses. In addition, the Board receives detailed information on all loans approved at the senior management level as well as status updates on the largest problem loans.

Loan Portfolio

The interest rates the Bank charges vary with the degree of risk, size, repricing frequency, and maturity of the loans. Competition from other financial services companies, the nature of the client’s deposit relationship with the Bank, and the Bank’s cost of funds impact the interest rate charged on loans.

Commercial Loans.    The Bank provides personalized financial services to the diverse commercial and professional businesses in its market areas. Commercial loans consist primarily of short-term loans (normally with a maturity of up to one year) to support business operations. The Bank focuses on businesses with annual revenues generally between $1.0 million and $100.0 million with borrowing needs generally between $2.0 million and $10.0 million. The Bank’s commercial clients represent a variety of manufacturing, technology, real estate, wholesale, and service businesses.

Commercial loans typically include revolving lines of credit collateralized by accounts receivable, inventory, and equipment. In underwriting commercial loans, we emphasize the borrower’s earnings history, cash flow, capitalization, leverage, and sources of repayment. In some instances, we require third party guarantees or highly liquid collateral (such as time deposits and investment securities). Commercial loan pricing is generally at a rate tied to the prime rate, as quoted in the Wall Street Journal.

The common risk associated with the commercial lending portfolio is the impact on our clients of weakness in the regional economy. Since the Bank’s community banking operations are concentrated in the San Francisco Bay Area, changes in the regional economy could materially impact loan performance and loan origination volumes. The Bank mitigates this risk by underwriting to conservative standards and by actively monitoring the credits.

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The Venture Banking Group, a division of the Bank, provides innovative lending products and other financial services tailored to the needs of start-up and development-stage companies. The Venture Banking Group’s typical clients include technology companies, such as multimedia, software, telecommunications providers, biotechnology, and medical device firms. Borrowings are generally secured by minimum cash balances, accounts receivable, intellectual property rights, inventory, and equipment. The financial strength of these companies also tends to be bolstered by the presence of venture capital investors among their shareholders. Because many of these companies are in the start-up or development phase, they may not generate any revenues for several years. As such, venture lending is riskier than traditional commercial lending. To mitigate this risk, we have implemented certain procedures specific to the venture lending practice. All venture lending is conducted by a specialized group of seasoned professionals with extensive experience in technology lending. The Venture Banking Group monitors its credits more frequently and extensively than is common for typical commercial credits. The maximum loan amount allowed for Venture Banking Group loans is lower than the maximum loan amount allowed for typical commercial credits. The overall exposure of the Venture Banking Group portfolio is relatively small, totaling $38.9 million at December 31, 2005, including $33.5 million of commercial loans.

We participate as a preferred lender in many SBA programs through the Greater Bay Bank SBA Lending Group. As a preferred lender, we have the ability to authorize, on behalf of the SBA, the SBA guaranty on loans under the SBA 7A program. Our status as a preferred lender results in more rapid turnaround of loan applications submitted to the SBA for approval compared to other lenders without that status. The SBA Lending Group utilizes both the 504 program, which is focused on longer-term financing of buildings and other long-term assets, and the 7A program, which is primarily used for financing equipment, inventory, and working capital for eligible businesses, generally over a three-to-seven-year term. The collateral position in SBA loans is enhanced by the SBA guaranty in the case of 7A loans, and by lower loan-to-value ratios under the 504 program. We have the ability to sell a portion of these loans to investors and retain the unguaranteed portion and servicing rights in our own portfolio. Federal guarantee support for the SBA programs depend on annual appropriations by the U.S. Congress. The primary risks associated with SBA lending relate to perfecting the lien on collateral and maintaining a valid guarantee. All SBA loans are originated and managed by a centralized unit. The SBA team consists of personnel with significant experience in originating, underwriting, and processing SBA loans. In order to ensure that required documentation is obtained, the SBA unit uses an SBA specific loan processing platform and quality control process.

We offer a complete range of financial products and services through our Matsco division to meet the needs of dentists and veterinarians. Matsco’s principal products include financing for practice start-up, practice expansion, practice acquisition, and working capital. These products are structured as either equipment leases or loans. In general, Matsco division loans are riskier than traditional commercial loans because underwriting decisions are heavily reliant on cash flow projections. Matsco mitigates this risk by developing policies and procedures specific to dental and veterinary practices.

We offer small ticket equipment lease financing through our Greater Bay Capital division. A risk associated with equipment lease financing is the effect of an economic downturn, particularly in the manufacturing sector. Another risk associated with this activity is estimating future residual values. We mitigate this uncertainty by assessing residual positions quarterly and by calculating residual impairment annually.

We offer asset-based lending and accounts receivable factoring products through Greater Bay Business Funding that provides alternative funding and support programs designed to enhance our small business banking services. This type of lending is potentially riskier than traditional commercial lending because the borrowers typically exhibit some type of financial weakness, such as negative net worth and/or operating losses. Greater Bay Business Funding has developed specific processes and procedures to address risk associated with this business activity. For example, these units underwrite both our clients and our clients’ customers. In most cases, these units purchase the receivables, closely monitor invoices, and control receipt of cash. As with the other Specialty Finance units, this specialized lending is performed by a dedicated group of professionals with specific expertise.

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Commercial Real Estate Term Loans.    The Bank provides medium-term commercial real estate loans secured by commercial or industrial buildings where the owner either uses the property for business purposes or derives income from tenants. Our loan policies require the principal balance of the loan, typically between $400,000 and $15.0 million, generally to be no more than 70%, or 80% for multiple-family residential properties, of the lower of actual or stabilized appraised value of the underlying real estate collateral at the loan’s inception. The loans, which are typically secured by first deeds of trust, generally have terms of no more than seven to ten years and are amortized over 20 to 25 years. Most of these loans have rates tied to the prime rate, with the majority structured to rate reset coincident with changes in the prime rate.

A primary risk associated with regional commercial real estate term lending is the effect of local economic conditions on loan portfolio credit quality. The Bank mitigates its exposure to San Francisco Bay Area economic conditions by underwriting to conservative standards. In addition, the Bank actively monitors concentrations in the commercial real estate portfolio on a quarterly basis and takes action to avoid building excess concentrations.

Real Estate Construction and Land Loans.    The Bank’s real estate construction loan activity primarily focuses on providing short-term loans (generally less than or equal to eighteen months to maturity) for the construction of real property in the Bank’s market areas to individuals and developers with whom the Bank has established relationships. Real estate construction loans for single-family residences to individuals typically range between approximately $500,000 and $1.0 million. Multi-family residential loans typically range between approximately $1.5 million and $5.0 million. Loans to developers for multi-unit single-family residential development projects typically are less than $500,000 per unit.

Residential real estate construction loans are typically secured by first deeds of trust and require personal guarantees of the principals or the developer. The economic strength of the project and the borrower’s creditworthiness are primary considerations in the loan underwriting decision. Generally, these loans provide above-average yields, but may carry a higher than normal risk of loss, particularly if general real estate values decline. To mitigate this risk, the Bank utilizes approved independent local appraisers. In addition, loan-to-value ratios at loan inception generally do not exceed 65% to 75% of the appraised value of the property. The Bank monitors projects during the construction phase through regular inspections and a disbursement schedule tied to the actual percentage of completion of each project.

The Bank also occasionally makes land loans to borrowers who intend to construct a single-family residence on the lot generally within 12 months. In addition, the Bank makes commercial real estate construction loans to high net worth clients with adequate liquidity. Such loans are typically secured by first deeds of trust and require personal guarantees of the principals or the developer.

Residential Mortgage Loans.    The residential mortgage loan portfolio is comprised primarily of pools of purchased loans. During 2005 and 2004, we purchased approximately $259.0 million of residential 30-year mortgage loans with hybrid interest features primarily located in California. More than half of the purchased loans are seasoned five-year fixed rate interest loans converting to one-year adjustable interest rate loans at the end of the five-year period. The remaining loans are ten-year fixed rate interest loans converting to adjustable interest rate loans at the end of the ten-year period. All of these loans were originated with loan to value (or “LTV”) ratios under 80% and a weighted average LTV of 60%. The Bank also originates residential mortgage loans.

Other Real Estate Loans.    Other real estate loans include equity lines of credit secured primarily by second deeds of trust on single-family residences. Most of these loans bear interest rates based on the prime rate and have terms of no more than 10 years.

Consumer and Other Loans.    The Bank’s consumer and other loan portfolio is divided between installment loans secured by automobiles and aircraft, home improvement loans, and lines of credit that are often secured by residential real estate. Installment loans are generally fixed rate with terms of one-to-five years, while the equity lines of credit and home improvement loans are generally floating rate and are reviewed for renewal annually. The Bank also has a limited portfolio of credit card lines issued as an additional service to our clients.

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We also provide a wide range of financial services to support the international banking needs of our clients, including providing international letters of credit, documentary collections, and other trade finance services. The Export-Import Bank of the United States has designated our International Banking Division as a “high” level lender to provide foreign receivable financing to local exporters. The Export-Import Bank allows “High” level delegated authority lenders to approve working capital loans up to $5.0 million per exporter and up to $75.0 million in the aggregate.

Deposit Gathering Activities

The Bank obtains deposits primarily from small and medium-sized businesses, business executives, professionals, and other individuals. The Bank offers the customary range of commercial depository products. The Bank’s deposits are diversified by source and product type. Rates paid on deposit categories vary due to different terms and conditions, individual deposit size, services rendered, and rates competitors pay on similar deposit products.

Insurance Brokerage Services Activities

Our insurance brokerage subsidiary, ABD, provides insurance brokerage, employee benefits consulting and risk management products and services to clients across the United States. ABD has 17 major offices in regional business centers across the western United States. ABD provides all lines of commercial property and casualty and employee benefits insurance coverage, as well as personal insurance (auto, homeowners and more) and 401(k) retirement plan consulting services. As of December 31, 2005, approximately 63% of ABD’s revenue was derived from property and casualty insurance services, 34% from employee benefits consulting services, and 3% from personal insurance services.

ABD specializes in servicing clients in the information technology, life sciences and healthcare, construction and real estate, public entities, agriculture and winemaking, maritime and marine, education, and hospitality industries. ABD also services clients outside of those specialized industries.

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Market Area

The Bank’s primary market areas are Alameda, Contra Costa, Marin, Monterey, Santa Clara, San Francisco, San Mateo, Santa Cruz, and Sonoma Counties. The following table provides information about our deposits and certain economic and demographic data for our market area.

The commercial base of our primary market areas is diverse and includes businesses engaged in computer and semiconductor manufacturing, professional services, biotechnology, printing and publishing, aerospace, defense, real estate construction, and wholesale and retail trade. As a result of our geographic concentration, our financial performance depends in part upon economic conditions in these areas. A protracted recovery or an economic downturn could have a material adverse impact on the quality of our loan portfolio and the demand for our products and services and, accordingly, on our results of operations. See “Item 1A—Risk Factors.”

While the majority of our community banking loan portfolio was originated in our primary market area, specialty finance lending activities are more national in scope.

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ABD provides commercial insurance brokerage, employee benefits consulting, and risk management solutions to business clients throughout the United States, with a concentration in the western United States.

Competition

The banking and financial services industry in California generally, and in the Bank’s market areas specifically, is highly competitive. The increasingly competitive environment is a result primarily of changes in regulation, changes in technology and product delivery systems, and the accelerating pace of consolidation among financial services providers. The Bank competes for loans, deposits, and customers with other commercial banks, savings and loan associations, securities and brokerage companies, mortgage companies, insurance companies, finance companies, money market funds, credit unions, and other nonbank financial service providers. Many of these competitors are much larger in total assets and capitalization, have greater access to capital markets, and offer a broader range of financial services than the Bank.

In order to compete with other financial services providers, the Bank principally relies upon local promotional activities, personal relationships established by relationship managers, officers, directors, and other employees, and specialized services tailored to meet the needs of the communities served. In those instances where the Bank is unable to accommodate a customer’s needs, the Bank may arrange for those services to be provided by its correspondents. The Bank has 41 branch offices located in Alameda, Contra Costa, Marin, Monterey, San Francisco, San Mateo, Santa Clara, Santa Cruz and Sonoma counties.

As of June 30, 2005, the latest date for which the Federal Deposit Insurance Corporation (or “FDIC”) branch data is available, the Bank’s deposits represented 2.1% of the deposits for all FDIC insured institutions in the San Francisco Bay Area, which includes Napa and Solano Counties in addition to the nine counties shown below. At that same date, the Bank’s deposits represented:

As in the banking and financial services industries, competition in the insurance brokerage industry is significant. ABD competes regularly against the largest global brokerage firms as well as regional firms for clients in the markets ABD targets. Nationally, ABD was ranked by Business Insurance Magazine as the 15th largest U.S. retail insurance broker during 2005, as well as being ranked among the top insurance brokers, based on premium or revenue volume, in most regional markets served.

Economic Conditions, Government Policies, Legislation, and Regulation

Our profitability, like most financial institutions, is primarily dependent on interest rate differentials. In general, the difference between the interest rates paid by us on interest-bearing liabilities, such as deposits and borrowings, and the interest rates received by us on our interest-earning assets, such as loans and investment securities, comprises the major portion of our earnings. These rates are sensitive to many external factors that are beyond our control, such as wholesale market interest rates levels, local competitive lending and deposit gathering conditions, wholesale credit spreads, and economic factors affecting borrowers’ repayment ability.

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Our business is also influenced by the monetary and fiscal policies of the federal government and the policies of regulatory agencies, particularly the Board of Governors of the Federal Reserve System (or “the Federal Reserve”). The Federal Reserve implements national monetary policies (with objectives such as curbing inflation and combating recession) through its open-market operations in U.S. Government securities, by adjusting the required level of reserves for depository institutions subject to its reserve requirements, and by varying the target federal funds and discount rates applicable to borrowings by depository institutions. The actions of the Federal Reserve in these areas influence the growth of bank loans, investments, and deposits and also affect interest rates earned on interest-earning assets and paid on interest-bearing liabilities. The nature and impact on us of any future changes in monetary and fiscal policies cannot be fully predicted.

From time to time, legislation, as well as regulations, are enacted that have the effect of increasing the cost of doing business, limiting or expanding permissible activities, or affecting the competitive balance between banks and other financial services providers. Proposals to change the laws and regulations governing the operations and taxation of banks, bank holding companies, and other financial institutions and financial services providers are frequently made in the U.S. Congress, in the state legislatures, and before various regulatory agencies. This legislation may change banking statutes and our operating environment in substantial and unpredictable ways. If enacted, such legislation could increase or decrease the cost of doing business, limit or expand permissible activities, or affect the competitive balance among banks, savings associations, credit unions, and other financial institutions. We cannot predict whether any of this potential legislation will be enacted, and if enacted, the effect that it, or any implementing regulations, would have on our financial condition or results of operations. In addition, litigation and investigations have been initiated by some state authorities that assert certain state laws are not preempted by Federal law and therefore such state laws apply to Federally chartered banks and thrifts. If changes result from these actions, Federally chartered banks like ours could be subject to additional regulatory compliance costs.

Supervision and Regulation

General.    Banks and bank holding companies are extensively regulated under both federal and certain state laws. This regulation is intended primarily for the protection of depositors and the deposit insurance fund and not for the benefit of stockholders of the financial institution. Set forth below is a summary description of the material laws and regulations that relate to our operations. The description is qualified in its entirety by reference to the applicable laws and regulations.

The Holding Company.    The holding company is a registered financial holding company subject to regulation and examination by the Federal Reserve under the Bank Holding Company Act of 1956, as amended (or “BHCA”). The holding company is required to file with the Federal Reserve periodic reports and such additional information as the Federal Reserve may require. The Federal Reserve’s bank holding company rating system emphasizes risk management and evaluation of the potential impact of nondepository entities on safety and soundness.

The Federal Reserve may require the holding company to terminate an activity or terminate control of or liquidate or divest certain subsidiaries, affiliates or investments if the Federal Reserve believes the activity or the control of the subsidiary or affiliate constitutes a significant risk to the financial safety, soundness or stability of our banking subsidiary. The Federal Reserve also has the authority to regulate provisions of certain bank holding company debt, including the authority to impose interest ceilings and reserve requirements on such debt. Under certain circumstances, the holding company must file written notice and obtain Federal Reserve approval prior to purchasing or redeeming equity securities. Further, the holding company is required by the Federal Reserve to maintain certain levels of capital. See “Capital Standards.”

The holding company is required to obtain prior Federal Reserve approval for the acquisition of more than 5% of the outstanding shares of any class of voting securities or substantially all of the assets of any bank or bank holding company. Prior Federal Reserve approval is also required for the merger or consolidation of the company and another bank holding company.

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The holding company is prohibited by the BHCA, except in certain statutorily prescribed instances, from acquiring direct or indirect ownership or control of more than 5% of the outstanding voting shares of any company that is not a bank or bank holding company and from engaging directly or indirectly in activities other than those of banking, managing or controlling banks, or furnishing services to its subsidiaries. However, subject to the prior Federal Reserve approval, the holding company may engage in any, or acquire shares of companies engaged in, activities that the Federal Reserve deems to be so closely related to banking or managing or controlling banks as to be a proper incident thereto. The holding company may also engage in these and certain other activities pursuant to its election as a financial holding company.

It is the policy of the Federal Reserve that each bank holding company serve as a source of financial and managerial strength to its subsidiary bank(s) and it may not conduct operations in an unsafe or unsound manner. A bank holding company’s failure to meet its obligations to serve as a source of strength to its subsidiary banks will generally be considered by the Federal Reserve to be an unsafe and unsound banking practice or a violation of Federal Reserve regulations or both.

Financial Holding Companies.    As a financial holding company, we may affiliate with securities firms and insurance companies and engage in other activities without prior Federal Reserve notice or approval that are determined to be financial in nature or are incidental or complementary to activities that are financial in nature. “Financial in nature” activities include:

In order to elect or retain financial holding company status, all of depository institution subsidiaries must be well-capitalized, well managed, and, except in limited circumstances, in satisfactory compliance with the Community Reinvestment Act. Failure to sustain compliance with these requirements or correct any non-compliance within a fixed time period could lead to divestiture of subsidiary banks or require us to conform all of our activities to those permissible for a bank holding company. A bank holding company that is not also a financial holding company can only engage in banking and such other activities determined by the Federal Reserve to be so closely related to banking or managing or controlling banks as to be a proper incident thereto.

The Bank.    As a national banking association, the Bank is subject to primary supervision, examination, and regulation by the Office of the Comptroller of the Currency (or “OCC”). The Bank is also subject to regulations of the FDIC as administrator of the deposit insurance funds, as well as certain regulations promulgated by the Federal Reserve. If, as a result of an examination of the Bank, the OCC should determine that the financial condition, capital resources, asset quality, earnings prospects, management, liquidity or other aspects of our operations are unsatisfactory or that we are violating or have violated any law or regulation, various remedies are available to the OCC. Such remedies include the power to enjoin “unsafe or unsound practices,” to require affirmative action to correct any conditions resulting from any violation or practice, to issue

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an administrative order that can be judicially enforced, to direct an increase in capital, to restrict our growth, to assess civil monetary penalties, and to remove officers and directors. The FDIC has similar enforcement authority, in addition to its authority to terminate the Bank’s deposit insurance in the absence of action by the OCC and upon a finding that we are operating in an unsafe or unsound condition, are engaging in unsafe or unsound activities, or that the Bank’s conduct poses a risk to the deposit insurance fund or may prejudice the interest of its depositors. See “Safety and Soundness Standards.”

Any changes in federal banking laws or the regulations of the banking agencies could have a material adverse impact on us, the Bank and our operations. For example in January 2006, the federal banking agencies jointly issued proposed guidance for banks and thrifts with high and increasing concentrations of commercial real estate (or “CRE”) construction and development loans. The implementation of these guidelines in final form could result in increased reserves and capital costs for banks and thrifts with “CRE concentration.” The Bank’s CRE portfolio as of December 31, 2005 would not meet the definition of CRE concentration as set forth in the proposed guidelines.

Interstate Banking and Branching.    Banks have the ability, subject to certain state restrictions, to acquire by acquisition or merger branches outside their home states. The establishment of new interstate branches is also possible in those states with laws that expressly permit it. Interstate branches are subject to certain laws of the states in which they are located. Competition may increase further as banks branch across state lines and enter new markets.

The Sarbanes-Oxley Act of 2002.    The Sarbanes-Oxley Act of 2002 addresses accounting oversight and corporate governance matters, including:

The legislation and its implementing regulations have resulted in increased costs of compliance, including certain outside professional costs.

Dividends and Other Transfers of Funds.    Dividends from the Bank and ABD constitute the principal source of income to the holding company. A Federal Reserve policy statement on the payment of cash dividends states that a bank holding company should pay cash dividends only to the extent that the holding company’s net income for the past year is sufficient to cover both the cash dividends and a rate of earnings retention that is consistent with the holding company’s capital needs, asset quality and overall financial condition. The Federal Reserve also indicated that it would be inappropriate for a company experiencing serious financial problems to borrow funds to pay dividends. Furthermore, under the federal prompt corrective action regulations, the Federal Reserve may prohibit a bank holding company from paying any dividends if the holding company’s bank subsidiary is classified as “undercapitalized.” See “Prompt Corrective Action” below.

The Bank and ABD are subject to various statutory and regulatory restrictions on their ability to pay dividends. Under such restrictions, the amount available for payment of dividends to the holding company by the Bank and ABD totaled $123.7 million and $1.9 million, respectively, at December 31, 2005. In addition, the Bank’s regulators have the authority to prohibit the Bank from paying dividends, depending upon the Bank’s financial condition, if such payment is deemed to constitute an unsafe or unsound practice.

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Capital Standards.    The federal banking agencies have adopted risk-based minimum capital guidelines intended to provide a measure of capital that reflects the degree of risk associated with a banking organization’s operations for both transactions reported on the balance sheet as assets and transactions that are recorded as off balance sheet items. Under these guidelines, nominal dollar amounts of assets and credit equivalent amounts of off balance sheet items are multiplied by one of several risk adjustment percentages, which range from 0% for assets fully backed by the Federal government, to 100% for assets with relatively high credit risk.

The risk-based capital ratio is determined by classifying assets and certain off-balance sheet financial instruments into weighted categories, with higher levels of capital being required for those categories perceived as representing greater risk. Under the capital guidelines, a banking organization’s total capital is divided into tiers. “Tier I capital” consists of (1) common equity, (2) qualifying noncumulative perpetual preferred stock, (3) a limited amount of qualifying cumulative perpetual preferred stock and (4) minority interests in the equity accounts of consolidated subsidiaries (including trust-preferred securities), less goodwill and certain other intangible assets. Qualifying Tier I capital may consist of trust-preferred securities, subject to the Federal Reserve’s final rule adopted March 4, 2005, which changed the criteria and quantitative limits for inclusion of restricted core capital elements in Tier I capital. “Tier II capital” consists of hybrid capital instruments, perpetual debt, mandatory convertible debt securities, a limited amount of subordinated debt, preferred stock that does not qualify as Tier I capital, a limited amount of the allowance for loan and lease losses and a limited amount of unrealized holding gains on equity securities. “Tier III capital” consists of qualifying unsecured subordinated debt. The sum of Tier II and Tier III capital may not exceed the amount of Tier I capital.

The risk-based capital guidelines require a minimum ratio of qualifying total capital to risk-adjusted assets of 8% and a minimum ratio of Tier 1 capital to risk-adjusted assets of 4% to be deemed adequately capitalized. In addition to the risk-based guidelines, federal banking regulators require banking organizations to maintain a minimum amount of Tier 1 capital to total assets, referred to as the leverage ratio. For a banking organization rated in the highest of the five categories used by regulators to rate banking organizations, the minimum leverage ratio of Tier 1 capital to total assets is 3%. A bank that does not achieve and maintain the required capital levels may be issued a capital directive by the FDIC to ensure the maintenance of required capital levels.

Prompt Corrective Action.    Federal banking agencies possess broad powers to take corrective and other supervisory action to resolve the problems of insured depository institutions, including but not limited to those institutions that fall below one or more prescribed minimum capital ratios. Each federal banking agency has promulgated regulations defining the following five categories in which an insured depository institution will be placed, based on its capital ratios:

The regulations use an institution’s risk-based capital and leverage capital ratios to determine the institution’s capital classification. An institution is treated as well-capitalized if its total capital to risk-weighted assets ratio is 10.00% or more; its core capital to risk-weighted assets ratio is 6.00% or more; and its core capital to adjusted total assets ratio is 5.00% or more. At December 31, 2005, the Bank’s capital ratios exceed these minimum percentage requirements for well-capitalized institutions.

An institution that, based upon its capital levels, is classified as well-capitalized, adequately capitalized, or undercapitalized may be treated as though it were in the next lower capital category if the appropriate federal banking agency, after notice and opportunity for hearing, determines that an unsafe or unsound condition or an unsafe or unsound practice warrants such treatment. At each successive lower capital category, an insured

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depository institution is subject to more restrictions. The federal banking agencies, however, may not treat a significantly undercapitalized institution as critically undercapitalized unless its capital ratio actually warrants such treatment.

Safety and Soundness Standards.    The federal banking agencies have adopted guidelines designed to assist the federal banking agencies in identifying and addressing potential safety and soundness concerns before capital becomes impaired. The guidelines set forth operational and managerial standards relating to: (i) internal controls, information systems and internal audit systems, (ii) loan documentation, (iii) credit underwriting, (iv) asset growth, (v) earnings, and (vi) compensation, fees and benefits. In addition, the federal banking agencies have also adopted safety and soundness guidelines with respect to asset quality and earnings standards. These guidelines provide six standards for establishing and maintaining a system to identify problem assets and prevent those assets from deteriorating. Under these standards, an insured depository institution should: (i) conduct periodic asset quality reviews to identify problem assets, (ii) estimate the inherent losses in problem assets and establish reserves that are sufficient to absorb estimated losses, (iii) compare problem asset totals to capital, (iv) take appropriate corrective action to resolve problem assets, (v) consider the size and potential risks of material asset concentrations, and (vi) provide periodic asset quality reports with adequate information for management and the board of directors to assess the level of asset risk. These guidelines also set forth standards for evaluating and monitoring earnings and for ensuring that earnings are sufficient for the maintenance of adequate capital and reserves.

Premiums for Deposit Insurance.    Through the Bank Insurance Fund (or “BIF”), the FDIC insures our customer deposits up to prescribed limits for each depositor. The amount of FDIC assessments paid by each BIF member institution is based on its relative risk of default as measured by regulatory capital ratios and other factors. Specifically, the assessment rate is based on the institution’s capitalization risk category and supervisory subgroup category. An institution’s capitalization risk category is based on the FDIC’s determination of whether the institution is well-capitalized, adequately capitalized or less than adequately capitalized. An institution’s supervisory subgroup category is based on the FDIC’s assessment of the financial condition of the institution and the probability that FDIC intervention or other corrective action will be required.

The assessment rate currently ranges from zero to 27 cents per $100 of domestic deposits. The FDIC may increase or decrease the assessment rate schedule on a semi-annual basis. Due principally to continued growth in deposits, the BIF is nearing its minimum ratio of 1.25% of insured deposits as mandated by law. If the ratio drops below 1.25%, it is likely the FDIC will be required to assess premiums on all banks. Any increase in assessments or the assessment rate could have a material adverse effect on earnings, depending on the amount of the increase. Furthermore, the FDIC is authorized to raise insurance premiums under certain circumstances.

The FDIC is authorized to terminate a depository institution’s deposit insurance upon a finding by the FDIC that the institution’s financial condition is unsafe or unsound or that the institution has engaged in unsafe or unsound practices or has violated any applicable rule, regulation, order or condition enacted or imposed by the institution’s regulatory agency.

All FDIC-insured depository institutions must pay an annual assessment to provide funds for the payment of interest on bonds issued by the Financing Corporation, a federal corporation chartered under the authority of the Federal Housing Finance Board. The bonds, commonly referred to as Financing Corporation Debt Obligations (or “FICO”) bonds, were issued to capitalize the Federal Savings and Loan Insurance Corporation. The FICO assessment rate for the fourth quarter of fiscal 2005 was 1.34 basis points for each $100 of assessable deposits. The FICO assessments are adjusted quarterly to reflect changes in the assessment bases of the FDIC’s insurance funds and do not vary depending on a depository institution’s capitalization or supervisory evaluations.

In February 2006, Congress enacted the Federal Deposit Insurance Reform Act of 2006 (or “FDIRA”), which provides, among other things, for the merger of the BIF and the SAIF into the Deposit Insurance Fund; future inflation adjustment increases in the standard maximum deposit insurance amount of $100,000; the increase of retirement account coverage to $250,000; changes in the formula and factors to be considered by the

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FDIC in calculating the FDIC reserve ratio, assessments and dividends, and a one-time aggregate assessment credit for depository institutions in existence on December 31, 1996 (or their successors) that paid assessments to recapitalize the insurance funds after the banking crises of the late 1980s and early 1990s. The FDIC is to issue regulations implementing the provisions of FDIRA. At this time it is uncertain what effect FDIRA and the forthcoming regulations will have on the Bank.

Loans-to-One Borrower Limitations.    With certain limited exceptions, the maximum amount that a national bank may lend to any borrower (including certain related entities of the borrower) at one time may not exceed 15% of the unimpaired capital and surplus of the institution, plus an additional 10% of unimpaired capital and surplus for loans fully secured by readily marketable collateral. At December 31, 2005, the bank’s loans-to-one-borrower limit was $131.1 million based upon the 15% of unimpaired capital and surplus measurement.

Transactions with Affiliates.    The Bank also is subject to certain restrictions imposed by Federal Reserve Act Sections 23A and 23B and Federal Reserve Regulation W on any extensions of credit to, or the issuance of a guarantee or letter of credit on behalf of, any affiliates, the purchase of, or investments in, stock or other securities thereof, the taking of such securities as collateral for loans, and the purchase of assets of any affiliates. Such restrictions prevent any affiliates from borrowing from us unless the loans are secured by marketable obligations of designated amounts. Further, such secured loans and investments by us to or in any affiliate are limited, individually, to 10.0% of our capital and surplus (as defined by federal regulations), and such secured loans and investments are limited, in the aggregate, to 20.0% of our capital and surplus. Some of the entities included in the definition of an affiliate are parent companies, sister banks, sponsored and advised companies, investment companies whereby the Bank’s affiliate serves as investment advisor, and financial subsidiaries of the Bank. Additional restrictions on transactions with affiliates may be imposed on us under the prompt corrective action provisions of federal law and the supervisory authority of the federal and state banking agencies. See “Prompt Corrective Action” and “Safety and Soundness Standards.”

USA PATRIOT Act.    The USA PATRIOT Act of 2001 and its implementing regulations significantly expanded the anti-money laundering and financial transparency laws. Under the USA PATRIOT Act, financial institutions are subject to prohibitions regarding specified financial transactions and account relationships, as well as enhanced due diligence and “know your customer” standards in their dealings with foreign financial institutions, foreign customers and private banking customers. For example, the enhanced due diligence policies, procedures, and controls generally require financial institutions to take reasonable steps:

Under the USA PATRIOT Act, financial institutions are required to establish and maintain anti-money laundering programs that include:

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The Bank has adopted comprehensive policies and procedures to address the requirements of the USA PATRIOT Act. Material deficiencies in anti-money laundering compliance can result in public enforcement actions by the banking agencies, including the imposition of civil money penalties and supervisory restrictions on growth and expansion. Such actions could have serious reputation consequences for the Company and the Bank.

Consumer Protection Laws and Regulations.    Examination and enforcement by the bank regulatory agencies for non-compliance with consumer protection laws and their implementing regulations have become more intense in nature. The Bank is subject to many federal consumer protection statutes and regulations, some of which are discussed below. Due to heightened regulatory concerns, the Bank may incur additional compliance costs or be required to expend additional funds for investment in its local community to comply with the following statutes and regulations.

The Home Ownership and Equal Protection Act of 1994 (or “HOEPA”) requires extra disclosures and consumer protections to borrowers for certain lending practices. The term “predatory lending,” much like the terms “safety and soundness” and “unfair and deceptive practices,” is far-reaching and covers a potentially broad range of behavior. Typically predatory lending involves at least one, and perhaps all three, of the following elements:

Privacy policies are required by federal banking regulations that limit the ability of banks and other financial institutions to disclose non-public information about consumers to nonaffiliated third parties. Pursuant to those rules, financial institutions must provide:

These privacy protections affect how consumer information is transmitted through diversified financial companies and conveyed to outside vendors.

In addition, state laws may impose more restrictive limitations on the ability of financial institution to disclose such information. California has adopted such a privacy law that among other things generally provides that customers must “opt in” before information may be disclosed to certain nonaffiliated third parties.

The Fair Credit Reporting Act, as amended by the Fair and Accurate Credit Transactions Act (or “FACT Act”) requires financial firms to help deter identity theft, including developing appropriate fraud response programs, and gives consumers more control of their credit data. In connection with FACT Act, financial institution regulatory agencies proposed rules that would prohibit an institution from using certain information about a consumer it received from an affiliate to make a solicitation to the consumer, unless the consumer has been notified and given a chance to opt out of such solicitations. A consumer’s election to opt out would be applicable for at least five years.

The Equal Credit Opportunity Act (or “ECOA”) generally prohibits discrimination in any credit transaction, whether for consumer or business purposes, on the basis of race, color, religion, national origin, sex, marital

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status, age (except in limited circumstances), receipt of income from public assistance programs, or good faith exercise of any rights under the Consumer Credit Protection Act.

The Truth in Lending Act (or “TILA”) is designed to ensure that credit terms are disclosed in a meaningful way so that consumers may compare credit terms more readily and knowledgeably. As a result of the TILA, all creditors must use the same credit terminology to express rates and payments, including the annual percentage rate, the finance charge, the amount financed, the total of payments and the payment schedule, among other things.

The Fair Housing Act regulates many practices, including making it unlawful for any lender to discriminate in its housing-related lending activities against any person because of race, color, religion, national origin, sex, handicap or familial status.

The Community Reinvestment Act (or “CRA”) is intended to encourage insured depository institutions, while operating safely and soundly, to help meet the credit needs of their communities. The CRA specifically directs the federal regulatory agencies, in examining insured depository institutions, to assess a bank’s record of helping meet the credit needs of its entire community, including low- and moderate-income neighborhoods, consistent with safe and sound banking practices. The CRA further requires the agencies to take a financial institution’s record of meeting its community credit needs into account when evaluating applications for, among other things, domestic branches, mergers or acquisitions, or holding company formations. The agencies use the CRA assessment factors in order to provide a rating to the financial institution. The ratings range from a high of “outstanding” to a low of “substantial noncompliance.” In its last examination for CRA compliance, as of November 2001, the Bank was rated “outstanding.”

The Home Mortgage Disclosure Act (or “HMDA”) grew out of public concern over credit shortages in certain urban neighborhoods and provides public information that will help show whether financial institutions are serving the housing credit needs of the neighborhoods and communities in which they are located. The HMDA also includes a “fair lending” aspect that requires the collection and disclosure of data about applicant and borrower characteristics as a way of identifying possible discriminatory lending patterns and enforcing anti-discrimination statutes.

The Real Estate Settlement Procedures Act (or “RESPA”) requires lenders to provide borrowers with disclosures regarding the nature and cost of real estate settlements. Also, RESPA prohibits certain abusive practices, such as kickbacks, and places limitations on the amount of escrow accounts. Penalties under the above laws may include fines, reimbursements and other penalties.

Insurance Brokerage Activities.    In every state in which ABD conducts business, the applicable office or an employee is required to be licensed or to have received regulatory approval by the state insurance department in order for ABD to conduct business. In addition to licensing requirements, most jurisdictions require individuals who engage in brokerage and certain insurance service activities to be licensed personally.

ABD’s insurance brokerage and risk management operations depend on its continued good standing under the licenses and approvals pursuant to which it operates. Licensing laws and regulations vary from jurisdiction to jurisdiction. In all jurisdictions, the applicable licensing laws and regulations are subject to amendment or interpretation by regulatory authorities. Generally such authorities are vested with relatively broad and general discretion as to the granting, renewing and revoking of licenses and approvals.

ABD has a subsidiary that is a registered broker dealer engaged primarily in mutual fund transactions on behalf of employee benefit plans of companies that are clients of ABD. The securities industry is subject to extensive regulation under both Federal and state laws. In addition, the Securities and Exchange Commission (or “SEC”), the National Association of Securities Dealers, Inc. (or “NASD”) other self-regulatory organizations (or “SROs”) such as the various stock exchanges, and other regulatory bodies, such as state securities commissions, require strict compliance with their rules and regulations. The SEC has delegated much of the regulation of broker-dealers to SROs, including the NASD, which is the primary regulatory of our broker dealer. The NASD also conducts periodic

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examinations of the operations of broker dealers. Our broker-dealer also is registered as a broker-dealer in a number of states and is subject to regulation by state securities administrators in states in which it conducts business. In addition, our broker-dealer is a member of the Securities Investor Protection Corporation, which provides certain protection for customers’ accounts in the event of the liquidation of a broker-dealer.

Employees

At December 31, 2005, we had 1,859 full-time employees. None of the employees is covered by a collective bargaining agreement. We consider our employee relations to be satisfactory.

Website

Our website address is www.gbbk.com. We make available free of charge on our website our annual report on Form 10-K, our quarterly reports on Form 10-Q, and our current reports on Form 8-K as soon as reasonably practicable after we file such reports with the SEC. None of the information on or hyperlinked from our website is incorporated into this Annual Report on Form 10-K.

ITEM 1A.    RISK FACTORS

In addition to the other information contained in this report, the following risks may affect us. If any of these risks occurs, our business, financial condition or operating results could be adversely affected.

Deterioration in economic conditions in the Bay Area could adversely affect our operations

Our Bay Area business concentration exposes us to changes in Bay Area economic conditions. Our operations are located in Northern California and concentrated primarily in Alameda, Contra Costa, Marin, Monterey, San Francisco, San Mateo, Santa Cruz, Santa Clara and Sonoma Counties, which include the area known as the “Silicon Valley.” As a result of this geographic concentration, our results are substantially affected by market, economic and business conditions in these areas.

Overall Bay Area economic trends continue to be of concern with the recovery from the 2000-2003 downturn being protracted. While there has been improvement in employment, real estate occupancy rates, and rental rates, these indicators all remain at levels below the peak of the economic boom the region enjoyed in the late 1990’s and remain depressed below levels that we would expect in a healthier economic environment. A further extended recovery period or a decline in economic and business conditions in our market areas, particularly in the technology and real estate industries on which the Bay Area depends, could have a material impact on the quality of our loan portfolio or the demand for our products and services, which in turn may have a material adverse effect on our results of operations.

Current investigations of the insurance industry by regulators may result in changes in industry practices that could have an adverse affect on our financial results

State attorneys general in several states are investigating insurance brokerage firms to obtain information about compensation agreements between insurance brokers and insurance companies. One of the areas of focus of these inquiries to date has been on contingency or override payments that insurance companies pay to brokers based on the overall relationship and services provided by the broker. Such payments are generally in accordance with longstanding industry practice and may be based upon a variety of factors, including, but not limited to, aggregate volume, profitability, and persistency of insurance policies placed by the broker. The New York Attorney General alleged that Marsh & McLennan Companies, Inc. engaged in illegal bid rigging and steering activities. The California Department of Insurance has also announced that, while it continues to review contingency arrangements, it is deferring any action on proposed broker compensation disclosure regulations in view of industry initiatives underway in this area.

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ABD receives such commissions and override payments, which amounted to $14.5 million during 2005, or 9.3% of total ABD commissions and fees. ABD has received requests for information from several state insurance commissioners and subpoenas from the Office of the Attorney General of the State of New York and the Office of the Attorney General of the State of Connecticut about ABD’s marketing practices and compensation arrangements with insurance carriers. As a result of conversations with officials of both states, it is our understanding that ABD’s receipt of the subpoenas is part of a broad review of the insurance brokerage industry and that others in the industry have received subpoenas. We anticipate that officials from other jurisdictions may also seek information from ABD as part of the ongoing industry-wide investigations into contingent commissions and override payments. ABD intends to cooperate in these investigations.

We have received no written comments regarding our periodic or current reports from the staff of the SEC that were issued 180 days or more preceding the end of our 2005 fiscal year and that remain unresolved.

We occupy our principal executive offices, located at 1900 University Avenue, 6^th Floor, in East Palo Alto, California, under a lease that expires in 2027, including options to renew. We continue to utilize our former executive offices located at 2860 West Bayshore Road in Palo Alto, California as an administrative facility.

We also operate 41 full service Bank branch offices and 23 additional properties for ABD, specialty finance, loan production, and administration offices. We own 8 of these properties and lease the other 56 properties. Most of the properties are located in the San Francisco Bay Area. These leases expire under various dates, including options to renew, through December 31, 2017.

We believe our present facilities are adequate for our current needs. We believe that, if necessary, we could secure suitable additional facilities on satisfactory terms.

From time to time, we are involved in certain legal proceedings arising in the normal course of our business. Management believes that the outcome of these matters will not have a material adverse effect on us.

There was no submission of matters to a vote of securities holders during the quarter ended December 31, 2005.

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PART II

Our common stock is traded on the Nasdaq under the symbol “GBBK.” The quotations shown below reflect for the periods indicated the high and low closing sales prices for our common stock as reported by Nasdaq.

There were 3,746 common shareholders of record and 131 convertible preferred shareholders of record at December 31, 2005.

For information on the ability of the Bank to pay dividends to the holding company, see “MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS—FINANCIAL CONDITION—Liquidity and Cash Flow” and Note 24 of the NOTES TO CONSOLIDATED FINANCIAL STATEMENTS.

On March 23, 2005, we announced a common stock repurchase program that authorized the purchase of up to and including $80.0 million of our common stock.

During 2005, we repurchased 2,326,347 shares of common stock for an aggregate amount of $60.0 million. The purchase price was allocated between common stock and retained earnings. Repurchased shares are available for reissuance. As of December 31, 2005, there was $30.7 million remaining under the 2005 common stock repurchase program to repurchase common stock.

Set forth below is certain information about repurchases of our common stock during the fourth quarter of 2005:

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The above table does not include 174,962 units of zero coupon contingent convertible debt securities (or “CODES due 2024”) ($175.0 million principal amount at maturity) that were repurchased for aggregate cash of $155.6 million during 2005. These repurchases were made in privately negotiated transactions. The repurchased CODES due 2024 were contingently convertible into an aggregate of 4,159,127 shares of our common stock, but were not convertible at the time of repurchase.

The above table also does not include 15,300 shares of Series B Preferred Stock that were repurchased for aggregate cash of $748,000 during 2005 at an average price paid per share of $48.87. These repurchases were made in privately negotiated transactions. The repurchased preferred stock was convertible into an aggregate of 25,551 shares of our common stock at the time of repurchase.

Information regarding Selected Financial Data appears on page A-1 under the caption “SELECTED FINANCIAL INFORMATION” and is incorporated herein by reference.

Information regarding Management’s Discussion and Analysis of Financial Condition and Results of Operations appears on pages A-2 through A-39 under the caption “MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS” and is incorporated herein by reference.

Information regarding Quantitative and Qualitative Disclosures About Market Risk appears on pages A-40 under the caption “QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK” and is incorporated herein by reference.

Information regarding Financial Statements and Supplementary Data appears on A-44 through A-48 under the caption “CONSOLIDATED BALANCE SHEETS,” “CONSOLIDATED STATEMENTS OF OPERATIONS,” “CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME,” “CONSOLIDATED STATEMENTS OF SHAREHOLDERS’ EQUITY,” “CONSOLIDATED STATEMENTS OF CASH FLOWS” and “NOTES TO CONSOLIDATED FINANCIAL STATEMENTS” and is incorporated herein by reference.

None.

Conclusion Regarding the Effectiveness of Disclosure Controls and Procedures

In accordance with Rule 13a-15(b) of the Exchange Act, we carried out an evaluation as of December 31, 2005 under the supervision and with the participation of our management, including our Chief Executive Officer and Chief Financial Officer, of the effectiveness of the design and operation of our disclosure controls and procedures as defined in Rule 13a-15(e) and 15d-15(e) under the Exchange Act. Based on that evaluation, our Chief Executive Officer and Chief Financial Officer have concluded that our disclosure controls and procedures are effective as of December 31, 2005.

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During the quarter ended December 31, 2005, there have been no changes in our internal controls over financial reporting that have materially affected, or are reasonably likely to materially affect, these controls. During 2005, we completed the systems integration of the 11 back-office systems of our former 11 banks into a single merged system. This integration did not result in any material changes in our internal control environment or our internal controls over financial reporting or cause any significant client disruption.

Report of Management on Internal Control Over Financial Reporting

The Report of Management on Internal Control Over Financial Reporting appears on A-41 under the caption “FINANCIAL STATEMENTS—REPORT OF MANAGEMENT ON INTERNAL CONTROL OVER FINANCIAL REPORTING.” Our independent auditors have issued an audit report on the report of management on internal control over financial reporting which appears on page A-42.

No information needs to be reported under this item since all required Form 8-K’s were filed during the fourth quarter of 2005.

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PART III

We intend to file a definitive proxy statement for the 2006 Annual Meeting of Shareholders (or “the Proxy Statement”) with the SEC within 120 days of December 31, 2005. Information regarding directors of Greater Bay will appear under the caption “DISCUSSION OF PROPOSALS—Proposal 1: “Election of Three Directors” in the Proxy Statement and is incorporated herein by reference. Information about Greater Bay’s Audit Committee Financial Expert will appear under the caption “INFORMATION ABOUT DIRECTORS AND EXECUTIVE OFFICERS—The Committees of the Board—Audit Committee” and is incorporated herein by reference. Information regarding compliance with Section 16(a) of the Securities Exchange Act of 1934, as amended, and executive officers will appear under the captions “INFORMATION ABOUT DIRECTORS AND EXECUTIVE OFFICERS—Section 16(a) Beneficial Ownership Reporting Compliance by Directors and Executive Officers” and “—Executive Officers” in the Proxy Statement and is incorporated herein by reference.

The holding company has adopted a code of ethics applicable to all of our directors and employees, including the principal executive officer, principal financial officer and principal accounting officer.

Information regarding executive compensation will appear under the captions “INFORMATION ABOUT DIRECTORS AND EXECUTIVE OFFICERS—How We Compensate Executive Officers,” “—How We Compensate Directors,” “—Employment Contracts, Change in Control Arrangements and Termination of Employment,” “—Compensation Committee’s Report on Executive Compensation,” “—Compensation Committee Interlocks and Insider Participation” and “—Performance Graph” in the Proxy Statement and is incorporated herein by reference.

The following table summarizes information as of December 31, 2005 relating to equity compensation plans of Greater Bay pursuant to which grants of options, restricted stock, or other rights to acquire shares may be granted from time to time.

Information regarding security ownership of certain beneficial owners and management and related shareholder matters will appear under the caption “INFORMATION ABOUT GREATER BAY BANCORP STOCK OWNERSHIP” in the Proxy Statement and is incorporated herein by reference.

Information regarding certain relationships and related transactions will appear under the caption “INFORMATION ABOUT DIRECTORS AND EXECUTIVE OFFICERS—Certain Relationships and Related Transactions” in the Proxy Statement and is incorporated herein by reference.

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Information regarding fees paid to PricewaterhouseCoopers LLP, our independent registered public accounting firm, will appear under the caption “DISCUSSION OF PROPOSALS—Proposal 4. Ratification of Selection of Independent Public Accounting Firm for 2006—Principal Auditor Fees and Services” in the Proxy Statement and is incorporated herein by reference.

PART IV

(a)    1.    Financial Statements

The following documents are filed as part of this report:

2.    Financial Statement Schedules

Not applicable.

3.    Exhibits

See Item 15(b) below. Exhibits 10.1(a) – (b), 10.2 (a) – (b), 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9(a) – (c), 10.10, 10.11, 10.13, 10.14, 10.15, 10.16, 10.17, 10.18, 10.19, 10.20, 10.21, 10.22, 10.23, 10.24, 10.25, 10.26, 10.27, 10.28 constitute managements contracts or compensatory benefit plans.

(b)    Exhibits Required by Item 601 of Regulation S-K

Reference is made to the Exhibit Index on pages 26 through 30 for exhibits filed as part of this report.

(c)    Additional Financial Statements

Not applicable.

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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, on the 22^nd day of March 2006.

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 in the capacities and on the dates indicated.

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EXHIBIT INDEX

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EXHIBIT INDEX (Continued)

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EXHIBIT INDEX (Continued)

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EXHIBIT INDEX (Continued)

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EXHIBIT INDEX (Continued)

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SELECTED FINANCIAL INFORMATION

The following table presents selected financial information as of December 31 of each of the last five years and for each of the five years periods ended December 31, 2005: