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As filed with the Securities and Exchange Commission on April 24, 2003

Registration No. 333-            

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

IMPAC MEDICAL SYSTEMS, INC.

(Exact Name of Registrant as Specified in Its Charter)

100 West Evelyn Avenue, Mountain View, California 94041

(650) 623-8800

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Joseph K. Jachinowski

President and Chief Executive Officer

IMPAC Medical Systems, Inc.

100 West Evelyn Avenue

Mountain View, California 94041

(650) 623-8800

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public:

As soon as practicable after this Registration Statement becomes effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act, check the following box.  ¨

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨                      

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨                      

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨                      

If delivery of the prospectus is expected to be made pursuant to Rule 434, please check the following box.  ¨

CALCULATION OF REGISTRATION FEE

The registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until this Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

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SUBJECT TO COMPLETION, DATED APRIL 24, 2003

The information in this prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission  is effective. This prospectus is not an offer to sell these securities, and it is not soliciting an offer to buy these securities in any state or jurisdiction where the offer or sale is not permitted.

2,158,500 Shares

Common Stock

IMPAC Medical Systems, Inc. is selling 200,000 shares of common stock and the selling stockholders identified in this prospectus are selling an additional 1,958,500 shares. We will not receive any of the proceeds from the sale of the shares by the selling stockholders. The selling stockholders have granted the underwriters a 30-day option to purchase up to an additional 323,775 shares from them to cover over-allotments, if any.

Our common stock is traded on the Nasdaq National Market under the symbol “IMPC.” The last reported sale price on April 24, 2003 was $19.00 per share.

INVESTING IN OUR COMMON STOCK INVOLVES RISKS. SEE “RISK FACTORS” BEGINNING ON PAGE 7.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

Thomas Weisel Partners LLC

U.S. Bancorp Piper Jaffray

William Blair & Company

The date of this prospectus is                 , 2003

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You should rely only on the information contained or incorporated by reference in this prospectus. We have not authorized anyone to provide you with information different from that contained in this prospectus. We are offering to sell shares of common stock and seeking offers to buy shares of common stock only in jurisdictions where offers and sales are permitted. The information contained in this prospectus is accurate only as of the date of this prospectus, regardless of the time of delivery of this prospectus or of any sale of the common stock.

In this prospectus, “Company,” “we,” “us” and “our” refer to IMPAC Medical Systems, Inc. and its subsidiaries. Unless otherwise indicated, all information in this prospectus assumes no exercise of the underwriters’ over-allotment option.

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PROSPECTUS SUMMARY

You should read the following summary together with the more detailed information concerning our company, the common stock being sold in this offering and our financial statements appearing in this prospectus. This prospectus contains forward-looking statements that involve risks and uncertainties. Because this is only a summary, you should read the rest of this prospectus before you invest in our common stock. Read this entire prospectus carefully, especially the risks described under “Risk Factors.”

IMPAC Medical Systems

We provide information technology systems for cancer care. Our systems provide electronic medical record, imaging, decision support, scheduling and billing applications in an integrated platform to manage the information-related complexities of cancer care, from detection and diagnosis through treatment and follow-up. Cancer centers require specialized information technology to administer complex treatments, to integrate advanced medical devices, to provide data aggregation and to meet reporting requirements. In addition to satisfying these needs, our systems improve the delivery of cancer care by enhancing patient safety, enabling advanced therapies, streamlining process management and facilitating communications.

We market and sell our systems to university teaching hospitals, community and government hospitals, freestanding cancer centers and private practices. Our information technology, or IT, solutions include point of care systems and cancer registry systems. In North America, we have sold and installed over 900 of our point of care systems and over 400 of our cancer registry systems in over 1,100 customer facilities. Based on our internal competitive analysis of the oncology IT market, we believe we have completed significantly more installations than our closest competitors. Our customers include 29 of the top 50 U.S. cancer hospitals, as ranked by U.S. News & World Report in July 2002. Outside of North America, our point of care systems are installed in approximately 400 facilities located in over 50 countries. Our modular design provides cancer centers the flexibility to fulfill their initial IT needs and easily expand their systems over time. We install our systems in facilities that range from small departments with less than five users to national delivery networks with hundreds of users.

Our business has grown steadily since our inception in 1990. Our net sales increased from $16.3 million for our fiscal year ended September 30, 1998 to $45.7 million for our fiscal year ended September 30, 2002, a compound annual growth rate of 29.3%. Our net sales increased from $20.4 million in the six months ended March 31, 2002 to $27.5 million in the six months ended March 31, 2003.

Industry Overview

Cancer is the second leading cause of death in the United States after heart disease. There are approximately 7,400 facilities in the United States that provide cancer treatment services. We believe there are also more than 4,000 accessible cancer treatment facilities outside the United States. These facilities provide surgery, chemotherapy and/or radiation therapy. Vendors in this market include companies whose primary business is oncology IT solutions, vendors who offer capital equipment with oncology IT solutions and healthcare IT providers that offer general solutions to all healthcare segments.

The treatment of cancer requires the precise coordination of many different healthcare practitioners who employ complex treatment methodologies, some of which can be extremely harmful or even fatal to the patient if administered improperly. These treatments are often administered in multiple settings

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and over an extended period of time. Additionally, these processes have intensive information management and billing requirements.

Many healthcare IT systems provide basic administrative and clinical functions, but do not satisfy the specialized requirements of cancer care.

Our Solution

Our IT solution provides the following benefits:

Our Strategy

The key elements of our strategy are:

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Corporate Information

We were incorporated in California as IMPAC Medical Systems, Inc. in January 1990, and we reincorporated as a Delaware corporation in November 2002. Our principal executive offices are located at 100 West Evelyn Avenue, Mountain View, California 94041, and our telephone number is (650) 623-8800. Our corporate website is www.impac.com. Information contained on our website does not constitute part of this prospectus.

IMPAC Medical Systems, Inc., IMPAC, the IMPAC logo and our product names are trademarks of IMPAC. All other brand names or trademarks appearing in this prospectus are the property of their respective holders.

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THE OFFERING

Unless otherwise noted, the information in this prospectus, including the information above:

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SUMMARY CONSOLIDATED FINANCIAL INFORMATION

(in thousands, except per share data)

The table below sets forth summary consolidated financial information for the periods indicated. This data has been derived from our audited consolidated financial statements for the years ended September 30, 2000, 2001 and 2002 and from our unaudited consolidated financial statements for the six months ended March 31, 2002 and 2003 and as of March 31, 2003 included elsewhere in this prospectus. The statements of operations data for the years ended September 30, 1998 and 1999 were derived from our audited consolidated financial statements that do not appear in this prospectus. It is important that you read this information together with the section entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our consolidated financial statements and the notes to them included elsewhere in this prospectus.

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RISK FACTORS

You should carefully consider the risks described below before making an investment decision. The risks described below are not the only ones we face. Additional risks we are not presently aware of or that we currently believe are immaterial may also impair our business operations. Our business could be harmed by any of these risks. The trading price of our common stock could decline due to any of these risks, and you may lose all or part of your investment. In assessing these risks, you should also refer to the other information contained in this prospectus, including our financial statements and related notes.

Risks Relating to Our Business

Our operating results may fluctuate significantly and may cause our stock price to decline.

We have experienced significant variations in revenues and operating results from quarter to quarter. Our quarterly operating results may continue to fluctuate due to a number of factors, including:

Because a significant percentage of our expenses will be relatively fixed, changes in the timing of sales and implementations could cause significant variations in operating results from quarter to quarter. We believe that period to period comparisons of our historical results of operations are not necessarily meaningful. You should not rely on these comparisons as indicators of our future performance.

Due to the length of our sales cycle, we are required to spend substantial time and expense before we are able to recognize revenue.

The sales cycle for our systems ranges from six to 24 months or more from initial contact to contract execution, and we may require an additional three to nine months to complete implementation. During this period, we will expend substantial time, effort and financial resources preparing contract proposals, negotiating the contract and implementing our systems. As a result, we may not realize any revenues from some customers after expending considerable resources. Even if we do realize revenues from a project, delays in implementation may keep us from recognizing these revenues during the same period in which sales and implementation expenses were incurred. This could cause our operating results to fluctuate from quarter to quarter.

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The majority of our sales has been into the radiation oncology market. If we are unable to expand outside the radiation oncology market or expand into international markets, our ability to grow will be limited.

Sales of our products into the radiation oncology market in the United States, including maintenance and services, represented approximately 72.1% of our net sales in the fiscal year ended September 30, 2002 and 71.5% in the six months ended March 31, 2003. Many of the largest radiation oncology facilities and practices in the United States have previously purchased our systems. To sustain our growth, we must expand our radiation oncology sales outside the United States and increase our sales outside of the radiation oncology market. We have expanded our product offerings domestically to address medical oncology, hospital and central registry data aggregation and reporting, and recently, laboratory information systems and urology. However, we may not be successful selling our products in international radiation oncology markets, or marketing our products in new markets.

If we are unable to integrate our products successfully with existing information systems and oncology treatment devices, or we are restricted from access to new device interfaces, customers may choose not to use our products and services.

For healthcare facilities to fully benefit from our products, our systems must integrate with the customer’s existing information systems and medical devices. This may require substantial cooperation, investment and coordination on the part of our customers. There is little uniformity in the systems and devices currently used by our customers, which complicates the integration process. If these systems are not successfully integrated, our customers could choose not to use, or to reduce their use of, our systems, which would harm our business.

Our ability to design systems that integrate applications, devices and information systems has been a key to our success in the radiation oncology market. Our competitors include manufacturers of radiation oncology equipment. If these manufacturers were to deny us access to new device interfaces, we would lose one of our key competitive advantages and our sales would be adversely impacted.

We operate in an intensely competitive market that includes companies that have greater financial, technical and marketing resources than we do, and companies who bundle their software with hardware sales at little or no additional cost, which makes it harder for us to sell our systems.

We operate in a market that is intensely competitive. Our principal oncology competitor is Varian Medical Systems, Inc. We also face competition from providers of enterprise level healthcare information systems, practice management systems, general decision support and database systems and other segment-specific software applications. In addition, although we have cooperative strategic arrangements with Siemens Medical Systems, Inc. and other companies for the sale of some of our products, these companies also compete with us on the sale of some of our products. A number of existing and potential competitors are more established than we are and have greater name recognition and financial, technical and marketing resources than we do.

Our most significant competitors also manufacture radiation oncology devices and other equipment used by healthcare providers who may be our potential customers. These particular competitors pose a competitive risk for us because they market their software with their hardware products as a bundled solution at little or no additional cost, which could enhance their ability to meet a potential customer’s needs. As a result, to make a sale, we must convince potential customers that our products are sufficiently superior to the software offered by the medical device manufacturer to justify the additional costs of purchasing our products. We also expect that competition will continue to increase, particularly if enterprise level healthcare software providers, such as Cerner Corporation and Eclipsys Corporation,

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choose to focus on the oncology market. As a result of increased competition, we may need to reduce the price of our products and services, and we may experience reduced gross margins or loss of market share, any one of which could significantly reduce our future revenues and operating results.

A decline in spending for healthcare information technology and services may result in less demand for our products and services, which could adversely affect our financial results.

The purchase of our products and services involves a significant financial commitment by our customers. The cost of our systems typically ranges from $75,000 to more than $500,000. At the same time, the healthcare industry faces significant financial pressures that could adversely affect overall spending on healthcare information technology and services. For example, the Balanced Budget Act of 1997 significantly reduced Medicare reimbursements to hospitals, leaving them less money to invest in infrastructure. Moreover, a general economic decline or further reductions in Medicare reimbursements to hospitals could cause hospitals to reduce or eliminate information technology-related spending. If spending for healthcare information technology and services declines or increases slower than we anticipate, demand for our products and services could decline, adversely affecting the prices we may charge.

Changing customer requirements could decrease the demand for our products, which could harm our business and adversely affect our revenues.

The market for our products and services is characterized by rapidly changing technologies, evolving industry standards and new product introductions and enhancements that may render existing products obsolete or less competitive. As a result, our position in the healthcare information technology market could erode rapidly due to unforeseen changes in the features, functions or pricing of competing products. Our future success will depend in part on our ability to enhance our existing products and services and to develop and introduce new products and services to meet changing customer requirements. The process of developing products and services such as those we offer is complex and in the future is expected to become increasingly more complex and expensive as new technologies and new methods of treating cancer are introduced. If we are unable to enhance our existing products or develop new products to meet changing customer requirements, including the introduction of new cancer treatment methods with which our products are not currently compatible, demand for our products could suffer.

We depend on our relationships with distributors and oncology equipment manufacturers to market our products, and if these relationships are discontinued, or we are unable to develop new relationships, our revenues could decline.

To successfully market and sell our products both in the United States and in foreign markets, we have developed relationships with distributors and leading oncology equipment manufacturers, including Siemens Medical Systems, Inc. Sales to Siemens represented 8.0% of our net sales in the six months ended March 31, 2003, 12.2% in fiscal 2002, 12.7% in fiscal 2001 and 14.6% in fiscal 2000. We rely on these collaborative relationships to augment our direct sales efforts and maintain market access to potential customers, particularly in Europe and Asia, and our business strategy includes entering into additional third-party relationships in the future. Some of these manufacturers and distributors also produce or distribute products that directly compete with our core products.

We may not be able to maintain or develop these relationships with distributors and oncology equipment manufacturers, and these relationships may not continue to be successful. If any of these relationships is terminated, not renewed or otherwise unsuccessful, or if we are unable to develop additional relationships, our sales could decline, and our ability to continue to grow our business could be adversely affected. This is particularly the case for our international sales, where we rely on our

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distributors’ expertise regarding foreign regulatory matters and their access to actual and potential customers. In many cases, these parties have extensive relationships with our existing and potential customers and influence the decisions of these customers. In addition, if these relationships fail, we will have to devote additional resources to market our products than we would otherwise, and our efforts may not be as effective as those of the distributors and manufacturers with whom we have relationships. We are currently investing, and plan to continue to invest, significant resources to develop these relationships. Our operating results could be adversely affected if these efforts with distributors and manufacturers do not generate revenues necessary to offset these investments.

We are subject to extensive federal, state and international regulations, which could cause us to incur significant costs.

Four of our medical device products, including two device connectivity products and two imaging products, are subject to extensive regulation by the U.S. Food and Drug Administration, or FDA, under the Federal Food, Drug and Cosmetic Act, or FDC Act, and by the Food and Drug Branch of the California Department of Health Services, or FDB, which is the California state agency that oversees compliance with FDA regulations. The FDA’s regulations govern product design and development, product testing, product labeling, product storage, premarket clearance or approval, advertising and promotion, and sales and distribution. Unanticipated changes in existing regulatory requirements or adoption of new requirements could hurt our business, financial condition and results of operations.

Numerous regulatory requirements apply to our medical device products, including the FDA’s Quality System Regulations, which require that our manufacturing operations follow design, testing, process control, documentation and other quality assurance procedures during the manufacturing process. We are also subject to FDA regulations regarding labeling, adverse event reporting, and the FDA’s prohibition against promoting products for unapproved or “off-label” uses.

We face the risk that a future inspection by the FDA or FDB could find that we are not in full regulatory compliance. Our failure to comply with any applicable FDA regulation could lead to warning letters, non-approvals, suspensions of existing approvals, civil penalties and criminal fines, product seizures and recalls, operating restrictions, injunctions and criminal prosecution. If we fail to take adequate corrective action in response to any FDA observation of noncompliance, we could face enforcement actions, including a shutdown of our manufacturing operations and a recall of our products, which would cause our product sales, operating results and business reputation to suffer.

To market and sell our products in countries outside the United States, we must obtain and maintain regulatory approvals and comply with the regulations of those countries. These regulations and the time required for regulatory review vary from country to country. Obtaining and maintaining foreign regulatory approvals is expensive and time consuming. We plan to apply for regulatory approvals in particular countries, but we may not receive the approvals in a timely way or at all in any foreign country in which we plan to market our products, and if we fail to receive such approvals, our ability to generate revenue will be harmed.

Our products could be subject to recalls even after receiving FDA approval or clearance. A recall would harm our reputation and adversely affect our operating results.

The FDA, FDB and similar governmental authorities in other countries in which we market and sell our products have the authority to require the recall of our products in the event of material deficiencies or defects in design or manufacture. A government mandated recall, or a voluntary recall by us, could occur as a result of component failures, manufacturing errors or design defects, including defects in labeling. A recall could divert management’s attention, cause us to incur significant expenses, harm our reputation with customers and negatively affect our future sales.

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Regulation of additional products of ours not currently subject to regulation as medical devices by the FDA could increase our costs, delay the introduction of new products and adversely affect our revenue growth.

The FDA has increasingly regulated computer products and computer-assisted products as medical devices under the FDC Act. If the FDA chooses to regulate any more of our products as medical devices, we would likely be required to take the following actions:

We may not be able to convince the FDA to grant approval to a request for market clearance. If any of our products fails to comply with FDA requirements, we could face FDA refusal to grant pre-market clearance or approval of products, withdrawal of existing FDA clearances and approvals, fines, injunctions or civil penalties, recalls or product corrections, production suspensions and criminal prosecution. FDA regulation of additional products could increase our operating costs, delay or prevent the marketing of new or existing products and adversely affect our revenue growth.

New and potential federal regulations relating to patient confidentiality could require us to redesign our products.

State, federal and foreign laws regulate the privacy and security of individually identifiable health information. Although compliance with these laws and regulations is presently the principal responsibility of the hospital, physician or other healthcare provider, we must ensure that our products and business operations support these requirements by providing adequate privacy and security protection to associated patient health information. Regulations governing electronic health data transmission, privacy and security are evolving rapidly and are often unclear and difficult to apply.

Of particular importance is the Health Insurance Portability and Accountability Act of 1996, or HIPAA. Under HIPAA, the Secretary of Health and Human Services, or HHS, has adopted national data interchange standards for some types of electronic transactions and the data elements used in those transactions; adopted security standards to protect the confidentiality, integrity, and availability of patient health information; and adopted privacy standards to prevent inappropriate access, use and disclosure of patient health information. In December 2000, HHS published the final privacy regulations, which took effect in April 2003. These regulations restrict the use and disclosure of individually identifiable health information without the prior informed consent of the patient. In February 2003, HHS published the final security regulations, which will take effect in April 2005. These regulations mandate that healthcare facilities implement operational, physical and technical security measures to reasonably prevent accidental, negligent or intentional inappropriate access or disclosure of patient health information. We have made changes to our products and business operations to support these regulatory requirements. We feel that our currently available products and operations fully support our customers’ requirements to comply with the above regulations. However, HHS enforcement efforts may find that our operations and product offerings are insufficient to support our customers’ regulatory requirements. A customer’s failure to meet any applicable HIPAA regulation could lead to fines, injunctions or criminal prosecution of the customer, which would cause our product sales and business reputation to suffer. Initial enforcement efforts and regulatory changes could also force us to redesign our products or further change our

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operations. We may incur significant product development costs to modify or redesign our products to address evolving data security and privacy requirements.

We cannot predict the potential impact of any rules that have not yet been proposed or any forthcoming changes to the newly enacted rules. In addition, other foreign, federal and/or state privacy and security legislation may be enacted at any time.

If our products fail to provide accurate and timely information to our customers in their treatment of patients, our customers may be able to assert claims against us that could result in substantial costs to us, harm our reputation in the industry and cause demand for our products to decline.

We provide products that assist clinical decision-making and relate to patient medical histories and treatment plans. If these products fail to provide accurate and timely information, customers may be able to assert liability claims against us. Any potential liability claims, regardless of their outcome, could result in substantial costs to us, divert management’s attention from operations and decrease market acceptance of our products. We attempt to limit by contract our liability for damages arising from negligence, errors or mistakes. Despite this precaution, the limitations of liability set forth in our contracts may not be enforceable or may not otherwise protect us from liability for damages. We maintain general liability insurance coverage, including coverage for errors or omissions. However, this coverage may not continue to be available on acceptable terms or may not be available in sufficient amounts to cover one or more large claims against us. In addition, the insurer might refuse coverage as to any future claim.

Highly complex software products such as ours often contain undetected errors or failures when first introduced or as updates and new versions are released. It is particularly challenging for us to test our products because it is difficult to simulate the wide variety of computing environments in which our customers may deploy them. Despite extensive testing, from time to time we have discovered defects or errors in our products. Defects, errors or difficulties could cause delays in product introductions and shipments, result in increased costs and diversion of development resources, require design modifications or decrease market acceptance or customer satisfaction with our products. In addition, despite testing by us and by current and potential customers, errors may be found after commencement of commercial shipments, which may result in loss of or delay in market acceptance of our products.

If we undertake additional acquisitions, they may be disruptive to our business and could have an adverse effect on our future operations and cause the market price of our common stock to decline.

An element of our business strategy has been expansion through acquisitions. Since 1997, we have completed six acquisitions of businesses or product lines. As a result of these acquisitions, we face the following risks:

If we pursue any future acquisitions, we will also face additional risks, including the following:

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Interruptions in our power supply or telecommunications capabilities or the occurrence of an earthquake or other natural disaster could disrupt our operations and cause us to lose revenues or incur additional expenses.

Our primary facilities are located in California near known earthquake fault zones and are vulnerable to significant damage from earthquakes. We are also vulnerable to damage from other types of disasters, including tornadoes, fires, floods, power loss, communications failures and similar events. If any disaster were to occur, our ability to operate our business at our facilities could be seriously impaired or destroyed. The insurance we maintain may not be adequate to cover our losses resulting from disasters or other business interruptions.

We currently do not have backup generators to be used as alternative sources of power in the event of a loss of power to our facilities. During any power outage, we would be temporarily unable to continue operations at our facilities. This would have adverse consequences for our customers who depend on us for system support and outsourcing services. Any such interruption in operations at our facilities could damage our reputation and harm our ability to obtain and retain customers, which could result in lost revenue and increased operating costs.

We have customers for whom we store and maintain critical patient and administrative data on computer servers in our application service provider, or ASP, data center. Those customers access this data remotely through telecommunications lines. If our back-up power generators fail during any power outage or if our telecommunications lines are severed or impaired for any reason, those customers would be unable to access their critical data causing an interruption in their operations. In such event our remote access customers and their patients could seek to hold us responsible for any losses. We may also potentially lose those customers and our reputation could be harmed.

If we fail to attract, motivate and retain highly qualified technical, marketing, sales and management personnel, our ability to operate our business could be impaired.

Our success depends, in significant part, upon the continued services of our key technical, marketing, sales and management personnel and on our ability to continue to attract, motivate and retain highly qualified employees. Competition for these employees is intense. In addition, the process of recruiting personnel with the combination of skills and attributes required to operate our business can be difficult, time-consuming and expensive. The success of our business depends to a considerable degree on our senior management team. The loss of any member of that team, particularly Joseph Jachinowski, James Hoey or David Auerbach, our founders, could hurt our business.

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We depend on licenses from third parties for rights to the technology used in several of our products. If we are unable to continue these relationships and maintain our rights to this technology, our business could suffer.

We depend upon licenses for some of the technology used in our products from a number of third-party vendors, including Pervasive Software Inc., Medicomp Systems, Inc., First DataBank, Inc., Crystal Decisions, Inc. and SoftVelocity, Inc. If we were unable to continue using the technology made available to us under these licenses on commercially reasonable terms or at all, we may have to discontinue, delay or reduce product shipments until we obtain equivalent replacement technology, which could hurt our business. In addition, if our vendors choose to discontinue support of the licensed technology in the future, we may not be able to modify or adapt our own products.

If we fail to protect our intellectual property, our business could be harmed.

We are dependent upon our proprietary information and technology. Our means of protecting our proprietary rights may not be adequate to prevent misappropriation. The laws of some foreign countries may not protect our proprietary rights as fully as do the laws of the United States. Also, despite the steps we have taken to protect our proprietary rights, it may be possible for unauthorized third parties to copy aspects of our products, reverse engineer our products or otherwise obtain and use information that we regard as proprietary. In some limited instances, customers can access source-code versions of our software, subject to contractual limitations on the permitted use of the source code. Although our license agreements with these customers attempt to prevent misuse of the source code, the possession of our source code by third parties increases the ease and likelihood of potential misappropriation of such software. Furthermore, others could independently develop technologies similar or superior to our technology or design around our proprietary rights. In addition, infringement or invalidity claims or claims for indemnification resulting from infringement claims could be asserted or prosecuted against us. Regardless of the validity of any claims, defending against these claims could result in significant costs and diversion of our resources. The assertion of infringement claims could also result in injunctions preventing us from distributing products. If any claims or actions are asserted against us, we might be required to obtain a license to the disputed intellectual property rights, which might not be available on reasonable terms or at all.

Our international sales, marketing and service activities expose us to uncertainties that could limit our growth and adversely affect our operating results.

In addition to our domestic operations, we currently conduct sales, marketing and service activities in other countries in North America, Europe and the Pacific Rim. Our international operations pose risks that include:

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If we are unable to meet and overcome these challenges, our international operations may not be successful, which would limit the growth of our business.

Risks Related to This Offering

Our common stock has been publicly traded since only November 2002, and the price of our common stock has fluctuated substantially.

Our common stock has been traded on a public market for less than six months. Since our initial public offering in November 2002, the closing sales price of our common stock has ranged from a low of $16.15 to a high of $23.25. A number of factors will continue to influence the market price for the common stock following this offering, including:

If the trading market for our stock does not continue to develop, securities analysts may not initiate or maintain research coverage of our company and our shares, and this could further depress the market for our shares.

A large number of shares may be sold into the market following this offering, which may cause the price of our common stock to decline.

After this offering, 9,587,024 shares of our common stock will be outstanding based upon shares outstanding as of March 31, 2003. The 2,158,500 shares we and certain stockholders are selling in this offering, and the 323,775 shares being offered by the selling stockholders if the underwriters exercise their over-allotment option in full, will be freely tradable, without restriction or further registration, under the federal securities laws unless purchased by our affiliates.

Certain of our stockholders holding an aggregate of 4,092,405 shares after this offering, assuming the underwriters do not exercise their over-allotment option, have agreed not to sell their shares of stock

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for 90 days after the completion of this offering. Thomas Weisel Partners LLC may waive any of these lock-up restrictions prior to the expiration of the lock-up period without prior notice. Thomas Weisel Partners LLC has no current intention to waive any of these lock-up restrictions. If, however, Thomas Weisel Partners LLC elects to waive such restrictions, all of these shares would be available for sale. Of the shares of common stock that will be available for sale the after the expiration of the lock-up period, or upon any election of Thomas Weisel Partners LLC to waive the lock-up restrictions, 3,588,821 will be subject to the volume restrictions of Rule 144 under federal securities laws because they are held by our affiliates.

If our common stockholders sell substantial amounts of common stock in the public market, or if the market perceives that these sales may be about to occur, the market price of our common stock could fall. After the completion of this offering, the holders of 287,537 shares of common stock will continue to have rights, subject to some conditions, to require us to file registration statements covering their shares, or to include their shares in registration statements that we may file for ourselves or for other stockholders. If these holders exercise their registration rights in one of our future registration statements, their stock sales could impair our ability to raise necessary capital by depressing the price at which we could sell our common stock.

Purchasers in this offering may experience additional dilution upon the exercise of outstanding options to purchase our common stock.

As of March 31, 2003, exercisable options to purchase a total of 854,658 shares of our common stock were outstanding under our stock option plans, with a weighted-average per share exercise price of $7.06. The exercise of all of these outstanding options would dilute the ownership percentage of purchasers in this offering by approximately 0.2% and may cause the market price of our common stock to decline.

Our executive officers and directors own a significant percentage of our stock, and as a result, the trading price for our shares may be depressed and these stockholders can take actions that may be adverse to your interests.

Following this offering, our executive officers and directors, and persons and entities affiliated with directors, will beneficially own approximately 40.3% of our common stock or approximately 37.9% if the underwriters exercise their over-allotment option in full. These stockholders, acting together, will have the ability to decide all matters requiring approval by our stockholders, including the election and removal of directors and any proposed merger, consolidation or sale of all or substantially all of our assets. In addition, they could dictate the management of our business and affairs. A significant concentration of share ownership can adversely affect the trading price for our common stock because investors often discount the value of stock in companies that have controlling stockholders. Furthermore, the concentration of ownership in our company could delay, defer or prevent a merger or consolidation, takeover or other business combination that could be favorable to you.

Anti-takeover provisions in our charter documents and Delaware law could prevent a potential acquiror from buying our stock.

Our certificate of incorporation and bylaws contain provisions that could delay or prevent a change in control of our company, including provisions that:

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In addition, we are governed by the provisions of Section 203 of Delaware General Corporation Law. These provisions may prohibit stockholders owning 15% or more of our outstanding voting stock from merging or combining with us. These and other provisions in our certificate of incorporation and bylaws, and under Delaware law, could discourage potential acquisition proposals, delay or prevent a change in control or management or reduce the price that investors might be willing to pay for shares of our common stock in the future.

INFORMATION REGARDING FORWARD-LOOKING STATEMENTS

This prospectus contains forward-looking statements, which may be deemed to include, but are not limited to, our business strategy, timing of and plans for the introduction of new products, services and enhancements, plans for hiring additional personnel, timing of and plans for opening new offices and the adequacy of anticipated sources of cash, including the proceeds from this offering, to fund our operations. Words such as “believes,” “anticipates,” “plans,” “expects,” “intends” and similar expressions are intended to identify forward-looking statements, but are not the exclusive means of identifying such statements. You should not place undue reliance upon these forward-looking statements, which apply only as of the date of this prospectus. Actual results could differ materially from those projected in any forward-looking statements for the reasons detailed in the “Risk Factors” portion of this prospectus beginning on page seven or elsewhere in this prospectus. We assume no obligation to update any forward-looking statement after the date of this prospectus.

This prospectus contains various estimates related to the IT and healthcare markets. These estimates have been included in studies published by market research and other firms. These estimates have been produced by industry analysts based on trends to date, their knowledge of technologies and markets, and customer research, but these are forecasts only and are thus subject to inherent uncertainty.

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USE OF PROCEEDS

We expect to receive net proceeds of approximately $3.0 million from the sale of 200,000 shares of common stock by us in this offering at an assumed public offering price of $19.00 per share after deducting underwriting commissions and discounts and estimated expenses. We will not receive any of the proceeds from the sale of shares by the selling stockholders.

We expect to use the net proceeds from this offering for working capital. The principal purpose of this offering is to provide liquidity for our existing stockholders.

PRICE RANGE OF COMMON STOCK

Our common stock has traded on the Nasdaq National Market under the symbol “IMPC” since our initial public offering on November 20, 2002. Prior to that time, there was no public market for our common stock. The following table sets forth, for the periods indicated, the high and low closing prices per share for our common stock as reported by the Nasdaq National Market since November 20, 2002:

On April 24, 2003, the last reported sale price of our common stock as reported on the Nasdaq National Market was $19.00 per share. As of March 31, 2003, there were approximately 59 holders of record of our common stock. Because many of our shares of common stock are held by brokers and other institutions on behalf of shareholders, we are unable to estimate the total number of shareholders represented by these record holders.

DIVIDEND POLICY

We have never declared or paid cash dividends on our capital stock. We currently intend to retain all available funds and any future earnings for use in the operation of our business and do not anticipate paying any cash dividends in the foreseeable future.

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CAPITALIZATION

The following table sets forth our capitalization at March 31, 2003 on an actual basis and on an as adjusted basis to give effect to the receipt of the estimated net proceeds from the sale of 200,000 shares of common stock offered by us in this offering at an assumed public offering price of $19.00 per share, after deducting underwriting discounts and commissions and estimated offering costs. The information below should be read in conjunction with our consolidated financial statements and the notes to those statements appearing elsewhere in this prospectus (in thousands, except share and per share data).

The number of shares of common stock listed in the table above excludes the following:

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SELECTED CONSOLIDATED FINANCIAL DATA

(in thousands, except per share data)

The following consolidated statements of operations data for the years ended September 30, 2000, 2001 and 2002 and consolidated balance sheet data as of September 30, 2001 and 2002 have been derived from our audited consolidated financial statements and related notes, which are included elsewhere in this prospectus. The statement of operations data for the six months ended March 31, 2002 and 2003 and the balance sheet data as of March 31, 2003 are derived from our unaudited consolidated financial statements included in this prospectus. The statements of operations data for the years ended September 30, 1998 and 1999 and the balance sheet data as of September 30, 1998, 1999 and 2000 were derived from our audited consolidated financial statements that do not appear in this prospectus. Our unaudited consolidated financial statements have been prepared by us on a basis consistent with our audited consolidated financial statements and, in management’s opinion, include all adjustments necessary, consisting only of normal recurring adjustments, for a fair presentation of this information. The consolidated statement of operations data for the six months ended March 31, 2003 and 2002 are not necessarily indicative of the results to be expected for the entire year, for any other interim period or for any future year. The consolidated selected financial data set forth below should be read in conjunction with our consolidated financial statements, the related notes and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” included elsewhere in this prospectus.

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