This filing is made pursuant
to Rule 424(b)(5) under
the Securities Act of 1933
in connection with
Registration Nos. 333-102512
and 333-105351

The selling stockholders named in this prospectus supplement are selling 1,880,000 shares of our common stock to a group of related institutional investors at a purchase price of $22.335 per share, for an aggregate purchase price of $41,989,800. PETCO will not receive any of the proceeds from the sale of shares of common stock by the selling stockholders.

Our common stock is listed on the Nasdaq National Market under the symbol "PETC." The last reported sale price of our common stock on the Nasdaq National Market on June 20, 2003 was $22.36 per share.

Investing in our common stock involves risks. See "Risk Factors" beginning on page S-4.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

You should rely only on the information contained or incorporated by reference in this prospectus supplement or the accompanying prospectus. We have not authorized anyone to provide you with different information. We are not making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. The information contained in this prospectus supplement and the accompanying prospectus is accurate only as of their respective dates, regardless of time of delivery of this prospectus supplement and the accompanying prospectus or of any sale of our common stock.

		Page
Prospectus Supplement
About this Prospectus Supplement		S-1
Prospectus Supplement Summary		S-2
Risk Factors		S-4
Cautionary Note Regarding Forward-Looking Statements		S-12
Use of Proceeds		S-13
Dividend Policy		S-13
Price Range of Common Stock		S-13
Selling Stockholders		S-14
United States Federal Income Tax Consequences to Non-U.S. Holders		S-16
Plan of Distribution		S-18
Legal Matters		S-18
Experts		S-18
Prospectus
About this Prospectus		3
Where You Can Find More Information		3
Cautionary Note Regarding Forward-Looking Statements		4
PETCO		5
Use of Proceeds		5
Selling Stockholders		6
Plan of Distribution		8
Description of Capital Stock		10
Legal Matters		11
Experts		11

This prospectus supplement is a supplement to the accompanying prospectus that is also a part of this document. This prospectus supplement and the accompanying prospectus are part of a registration statement that we filed with the Securities and Exchange Commission using a "shelf" registration process. Under this shelf registration process, we may sell common stock from time to time in one or more offerings up to a total dollar amount of $55 million and certain selling stockholders referred to in the prospectus may also offer and sell shares of our common stock. We will not receive any of the proceeds from any sales of shares by the selling stockholders. In this prospectus supplement, we provide you with specific information about the terms of this offering and certain other information. Both this prospectus supplement and the accompanying prospectus include important information about us, the selling stockholders, our common stock and other information you should know before investing in our common stock. This prospectus supplement and the accompanying prospectus also incorporate important business and financial information about PETCO Animal Supplies, Inc. and its subsidiaries that is not included in or delivered with these documents. You should read both this prospectus supplement and the accompanying prospectus as well as the additional information described under the heading "Where You Can Find More Information" on page 3 of the accompanying prospectus before investing in our common stock. This prospectus supplement adds, updates and changes information contained in the accompanying prospectus and the information incorporated by reference. To the extent that any statement that we make in this prospectus supplement is inconsistent with the statements made in the accompanying prospectus or the information incorporated by reference, the statements made in the accompanying prospectus are deemed modified or superseded by the statements made or incorporated by reference in this prospectus supplement.

Market data used throughout this prospectus supplement, including information relating to our relative position in the pet food, supplies and services retailing industry, is based on the good faith estimates of management, which estimates are based upon their review of internal surveys, independent industry publications and other publicly available information, including Packaged Facts reports and information prepared by the American Pet Products Manufacturers Association, the American Veterinary Medical Association, and the Business Communications Company, Inc. Although we believe that these sources are reliable, we do not guarantee the accuracy or completeness of this information, and we have not independently verified this information.

We own or have rights to trademarks or trade names that we use in conjunction with the operation of our business. In addition, our name, logo and web site name and address are our service marks or trademarks. Each trademark, trade name or service mark of any other company appearing in this prospectus supplement belongs to its holder. For example, Iams® and Eukanuba® are trademarks of The Iams Company, Science Diet® is a trademark of Hill's Pet Nutrition Inc. and Nutro® is a trademark of Nutro Products, Inc.

This summary highlights information contained elsewhere in this prospectus supplement. We urge you to read this entire prospectus supplement and the accompanying prospectus carefully, including the "Risk Factors" section. In this prospectus supplement and the accompanying prospectus, "PETCO Animal Supplies," "PETCO," "we," "our" and "us" refer to PETCO Animal Supplies, Inc. and its subsidiaries, unless the context requires otherwise. Unless indicated otherwise, all store counts are as of May 3, 2003. Our fiscal year ends on the Saturday closest to January 31, resulting in years of either 52 or 53 weeks. For example, fiscal 2002 consisted of 52 weeks ended on February 1, 2003.

We are a leading specialty retailer of premium pet food, supplies and services with 617 stores in 43 states and the District of Columbia. Our products include pet food, supplies, grooming products, toys, novelty items and vitamins, small pets such as fish, birds and other small animals (excluding cats and dogs), and veterinary supplies. Our strategy is to offer our customers a complete assortment of pet-related products and services at competitive prices, with superior levels of customer service at convenient locations.

Our stores combine the broad merchandise selection and everyday low prices of a pet supply warehouse store with the convenient location and knowledgeable customer service of a neighborhood pet supply store. We believe that this combination differentiates our stores and provides us with a competitive advantage. Our principal format is a 12,000 to 15,000 square foot store, conveniently located near local neighborhood shopping destinations, including supermarkets, bookstores, coffee shops, dry cleaners and video stores, where our target "pet parent" customer makes regular weekly shopping trips. We believe that our stores are well positioned, both in terms of product offerings and location, to benefit from favorable long-term demographic trends, a growing pet population and an increasing willingness of pet owners to spend on their pets.

Our corporate headquarters are located at PETCO Animal Supplies, Inc., 9125 Rehco Road, San Diego, CA 92121, and our telephone number is (858) 453-7845. Our web site address is www.petco.com. The information contained or incorporated in our web site is not a part of this prospectus supplement or the accompanying prospectus.

Unless otherwise indicated, all share information in this prospectus supplement is based on the number of shares outstanding as of June 13, 2003 and:

The value of an investment in PETCO will be subject to significant risks inherent in our business. You should carefully consider the risks and uncertainties described below and other information included in this prospectus supplement and the accompanying prospectus before purchasing our common stock. If any of the events described below occur, our business and financial results could be adversely affected in a material way. This could cause the trading price of our common stock to decline, perhaps significantly.

If we are unable to profitably open and operate new stores, maintain the profitability of our existing stores and successfully complete our store remodel program, our business, financial condition and results of operations may be harmed.

One of our strategies is to open new stores by focusing on both existing markets and by targeting new geographic markets. We have opened approximately 40 to 60 stores per year (offset by closings and relocations of existing stores) between fiscal 1998 and fiscal 2002. We plan to increase our net store count by 40 to 50 stores per year and plan to target one or two new geographic markets per year.

There can be no assurance that we will be able to open stores at this rate. The rate of our expansion will depend on several factors, including general economic and business conditions affecting consumer confidence and spending, the availability of desirable locations, the negotiation of acceptable lease terms, the availability of qualified personnel and our ability to manage the operational aspects of our growth. The rate of our expansion will also depend on the availability of adequate capital, which in turn will depend in large part on cash flow generated by our business and the availability of equity and debt capital. There can be no assurance that we will be able to obtain equity or debt capital on acceptable terms or at all. Moreover, our senior credit facility and the indenture governing our senior subordinated notes contain provisions that restrict the amount of debt we may incur in the future. If we are not successful in obtaining sufficient capital, we may be unable to open additional stores as planned, which may adversely affect our results of operations.

Our continued growth also depends, to a significant degree, on our ability to increase sales in our new and existing stores. Our comparable store net sales increased by 6.4%, 8.6% and 8.0% for fiscal 2000, 2001 and 2002, respectively, and by 4.6% for the first thirteen weeks of fiscal 2003. As a result of new store openings in existing markets and because mature stores will represent an increasing proportion of our store base over time, our comparable store net sales increases in future periods may be lower than historical levels.

There also can be no assurance that our existing stores will maintain their current levels of sales and profitability or that new stores will generate sales levels necessary to achieve store-level profitability, much less profitability comparable to that of existing stores. New stores that we open in our existing markets may draw customers from our existing stores and may have lower sales growth relative to stores opened in new markets. New stores also may face greater competition and have lower anticipated sales volumes relative to previously opened stores during their comparable years of operations. These factors, together with increased pre-opening expenses at our new stores, may reduce our average store contribution and operating margins. In addition, we are opening new stores in, and are remodeling some of our existing stores into, our millennium format, which incorporates our most recent merchandising strategies. There can be no assurance that our millennium format will be as or more profitable than our existing stores, and may be less profitable than historical levels for our other stores. If we are unable to profitably open and operate new stores and maintain the profitability of our existing stores, our business, financial condition and results of operations may be harmed.

We may be unable to successfully execute our expansion strategy or manage and sustain our growth and, as a result, our business may be harmed.

Our senior credit facility and the indenture governing our senior subordinated notes also contain covenants which may restrict or impair our growth plans. We currently expect to finance our store expansion plans from cash flow from operations, lease financing and capacity under our senior credit facility. To the extent that we are unable to obtain adequate financing for new store growth on acceptable terms, our ability to open new stores will be negatively impacted. As a result, there can be no assurance that we will be able to achieve our current plans for the opening of new stores. In addition, our failure to expand our distribution facilities or other internal systems or procedures in accordance with our growth plans, or difficulties we may incur in operating our distribution facilities, could adversely affect our ability to deliver merchandise to our stores in a timely fashion. As a result, our ability to support our planned new store growth may be harmed.

In addition, we routinely evaluate our strategic alternatives with respect to each of our stores and our other operating assets and investments. In connection with this evaluation, we may elect to close stores or to sell or otherwise dispose of selected assets or investments. Excluding store relocations, we closed ten stores in fiscal 2000, six stores in fiscal 2001, six stores in fiscal 2002 and two stores in the first thirteen weeks of fiscal 2003. There can be no assurance that any future sale or disposition would be achieved on terms favorable to us because we incur closing costs or may lose sales to our competitors as a result.

Our substantial amount of debt may limit the cash flow available for our operations and place us at a competitive disadvantage.

We have, and will continue to have, a substantial amount of debt. As of May 3, 2003, this debt consisted primarily of (1) $192.0 million of borrowings under our senior credit facility (with $56.2 million of additional available credit, subject to certain conditions) and (2) $170.0 million in principal amount of our senior subordinated notes. Our level of indebtedness has important consequences to you and your investment in our common stock. For example, our level of indebtedness may:

The agreement governing our senior credit facility and the indenture governing our senior subordinated notes contain a number of covenants imposing significant restrictions on our business. These restrictions may affect our ability to operate our business and may limit our ability to take advantage of potential business opportunities as they arise. These covenants place restrictions on our ability to, among other things:

If compliance with our debt obligations materially hinders our ability to operate our business and adapt to changing industry conditions, we may lose market share, our revenue may decline and our operating results may suffer.

Our failure to satisfy covenants in our debt instruments would cause a default under those instruments.

In addition to imposing restrictions on our business and operations, our debt instruments include a number of covenants relating to financial ratios and tests. Our ability to comply with these covenants may be affected by events beyond our control, including prevailing economic, financial and industry conditions. The breach of any of these covenants would result in a default under these instruments. An event of default would permit our lenders to declare all amounts borrowed from them to be due and payable, together with accrued and unpaid interest. Moreover, the lenders under our senior credit facility would have the option to terminate any obligation to make further extensions of credit under our senior credit facility. If we are unable to repay debt to our senior lenders, these lenders could proceed directly against our assets.

The loss of any of our three key vendors, or of our exclusive distribution arrangements with our vendors, would negatively impact our business.

We purchase significant amounts of products from three key vendors: The Iams Company, Hill's Pet Products, Inc. (which produces Science Diet) and Nutro Products, Inc. Supplies of products from these vendors accounted for approximately 9%, 10% and 8%, respectively, of our net sales in fiscal 2001 and 8%, 9% and 8%, respectively, in fiscal 2002. We do not maintain long-term supply contracts with any of our vendors. While we believe that our vendor relationships are satisfactory, any vendor could discontinue selling to us at any time. The loss of any of our three key vendors or any other significant vendors of premium pet food or pet supplies offered by us would have a negative impact on our business, financial condition and results of operations.

In addition, a change in how our key products are distributed could have a material adverse effect on our business. It could materially adversely affect our business if any premium pet food manufacturers were to make premium pet food products widely available in supermarkets or through

mass merchants, or if the premium brands currently available to supermarkets and mass merchants were to increase their market share at the expense of the premium brands sold only through specialty pet food and supplies retailers.

Through the end of fiscal 1999, the premium pet food brands that we purchased from The Iams Company, Hill's Pet Products, Inc. and Nutro Products, Inc. were not widely available in supermarkets or mass merchants. One of our primary premium pet food vendors, The Iams Company, was purchased by Procter & Gamble in fiscal 1999. In March 2000, Procter & Gamble broadened the distribution of the Iams brand to supermarkets, warehouse clubs and mass merchants across the country. The Eukanuba brand of pet food, which is also manufactured by The Iams Company, continues to be sold exclusively through specialty channels such as PETCO. Sales of Iams brand pet food represented approximately 9% of our net sales in fiscal 1999, decreasing to approximately 6% of our net sales in fiscal 2000. The broadening of the distribution of Iams brand pet food negatively impacted our comparable store net sales during fiscal 2000, resulting in lower increases in comparable store net sales through the first quarter of 2001.

Our principal vendors also currently provide us with certain incentives such as volume purchasing, trade discounts, cooperative advertising and market development funds. A reduction or discontinuance of these incentives would increase our costs and could reduce our profitability.

We also purchase significant amounts of pet supplies from a number of vendors with limited supply capabilities. There can be no assurance that our current pet supply vendors will be able to accommodate our anticipated growth and expansion of our stores. We continually seek to expand our base of pet supply vendors and to identify new pet-related products. An inability of our existing vendors to provide products in a timely or cost-effective manner could impair our business, financial condition and results of operations.

Competition in the markets in which we operate is strong and if we are unable to compete effectively, our ability to generate sales may suffer and our operating income and net earnings would decline.

The pet food and supplies retailing industry is highly competitive. We compete with a number of specialty pet store chains and traditional pet stores. We also compete with supermarkets, warehouse clubs and mass merchants. Many of these competitors are larger and have access to greater capital and management resources than we do.

There can be no assurance that in the future we will not face greater competition from national, regional and local retailers. In particular, if any of our major competitors seeks to gain or retain market share by reducing prices or by introducing additional products, we may be required to reduce prices on our key products in order to remain competitive, which may negatively impact our profitability.

A prolonged economic downturn could result in reduced sales and lower revenues and profitability.

Purchases of pet-related supplies may be affected by prolonged, negative trends in the general economy that adversely affect consumer spending. Any reduction in consumer confidence or disposable income in general may affect companies in pet-related and other retail industries more significantly than companies in industries that rely less on discretionary consumer spending. In addition, due to our substantial amount of debt, we are more susceptible to some of these adverse economic effects than are some of our competitors which have greater financial and other resources than we do.

Our operating results could be harmed if we are unable to integrate acquired companies into our operations.

The pet food and supplies retailing industry is highly fragmented. We may pursue expansion and acquisition opportunities in the future, and we must efficiently integrate and combine operations of

acquired companies to realize the anticipated benefits of acquisitions. To be successful, the integration process requires us to achieve the benefits of combining the companies, including generating operating efficiencies and synergies and eliminating or reducing redundant costs. Since we often have limited prior knowledge of acquired companies, there can be no assurance that the anticipated benefits of these acquisitions will be fully realized without incurring unanticipated costs or diverting management's attention from our core operations. Our operating results could be harmed if we are unable to efficiently integrate newly acquired companies into our operations. Any future acquisitions also could result in potentially dilutive issuances of equity securities, or the incurrence of additional debt or the assumption of contingent liabilities.

We have made investments in the past and may make investments in the future without being able to achieve an adequate return, if any, on our investment.

In the past we have made, and in the future we may make, investments in strategic ventures or other complementary businesses in an effort to expand internationally or to otherwise grow our business. These investments typically involve many of the same risks posed by acquisitions, particularly those risks associated with the diversion of our resources, the inability of the new venture to generate sufficient revenues, the management of relationships with third parties and potential expenses. Strategic ventures have the added risk that the other strategic venture partners may have economic, business or legal interests or objectives that are inconsistent with our interests and objectives. Although we have no present plans to make any such investment, there can be no assurance that any investment we make in the future would achieve an adequate return, if any.

In the past we have terminated, and in the future we may terminate, our relationship in a strategic venture after we have made substantial investments in that strategic venture. For example, our investment in Petopia.com, an e-commerce destination for the sale of pet food and supplies, failed to achieve the desired results, and in fiscal 2000 we took a charge of approximately $10.2 million due to Petopia.com's pending liquidation and wrote off $1.3 million in receivables due from Petopia.com. In addition, in January 2002 we terminated our relationship with Canadian Petcetera Limited Partnership, which operated 32 Petcetera retail pet food and supplies stores in Canada, because the stores operated by the Canadian partnership were not producing the results we had anticipated. At the time of the termination of our relationship, we also entered into a settlement agreement with the other partners of the partnership to resolve allegations made by the other partners that we had reneged on an alleged agreement to buy out their interests in the Canadian partnership. We recorded a write-off of approximately $26.7 million in the fourth quarter of fiscal 2001, which represented the carrying value of our Canadian investment and related assets, and settlement expenses of approximately $10.3 million related to the settlement of the related dispute.

If we are required to restructure our operations to comply with regulations governing our business, it could have a material effect on our business and operations.

The transportation and sale of small animals is governed by various state and local regulations. These laws vary from state to state and are enforced by the courts and by regulatory authorities with broad discretion. While we seek to structure our operations to comply with the laws and regulations of each state in which we operate, there can be no assurance that, given varying and uncertain interpretations of these laws, we would be found to be in compliance in all states. A determination that we are in violation of applicable laws in any state in which we operate could require us to restructure our operations to comply with the requirements of that state, which could have a material adverse effect on our business and operations.

Negative publicity arising from claims that we do not properly care for animals we sell could adversely affect how we are perceived by the public and reduce our revenues and profitability.

From time to time, we are subject to claims or complaints that we do not care properly for some of the animals we sell. For example, allegations were made in a complaint filed in June 2002 in the San Francisco Superior Court by the San Francisco City Attorney's office to the effect that certain associates have not properly cared for companion animals for sale in our two San Francisco stores. The complaint seeks damages, penalties and an injunction against the sale of companion animals in our San Francisco stores. The complaint and related news reports have caused negative publicity. We take seriously any allegations regarding the proper care of companion animals and have taken steps to reiterate to all our associates the importance of proper care for all companion animals in all our stores. We are responding to the complaint and are defending it vigorously. The complaint and any similar allegations or actions which could be filed in the future could cause negative publicity which could have a material adverse effect on our results of operations.

Some of our compensation practices have been challenged in a complaint that, if successful, could harm our financial condition and results of operations.

In July 2001, we received a copy of a complaint filed in the Superior Court of California for the County of Los Angeles alleging violations of the California Labor Code and the Business and Professions Code. The purported class of plaintiffs alleged that we improperly classified our salaried store managers and assistant store managers as exempt employees not entitled to overtime pay for work in excess of 40 hours per week. The relief sought includes compensatory damages, penalties, preliminary and permanent injunctions requiring us to pay overtime compensation under California law, prejudgment interest, costs and attorneys' fees and such other relief as the court deems proper. In November 2001, the case was transferred to the Superior Court of California for the County of San Diego. In December 2002, we announced our intention to settle all claims related to this lawsuit. While we continue to deny the allegations underlying the lawsuit, we have tentatively agreed to the settlement to avoid possible disruption to our business from protracted litigation. In fiscal 2002, we expensed $2.1 million, after tax, for the settlement, which received preliminary court approval but remains subject to final court approval. If the settlement is not approved, and the plaintiffs are successful, this litigation could further harm our financial condition, and any required change in our labor practices could have a negative impact on our results of operations.

We depend on key personnel, and if we lose the services of any of our principal executive officers, including Mr. Devine, our Chairman, President and Chief Executive Officer, we may not be able to run our business effectively.

We are dependent upon the efforts of our principal executive officers. In particular, we are dependent upon the management and leadership of Brian K. Devine, our Chairman, President and Chief Executive Officer. The loss of Mr. Devine or certain of our other principal executive officers could affect our ability to run our business effectively.

Our success will depend on our ability to retain our current management and to attract and retain qualified personnel in the future. Competition for senior management personnel is intense and there can be no assurance that we can retain our personnel. The loss of a member of senior management requires the remaining executive officers to divert immediate and substantial attention to seeking a replacement. The inability to fill vacancies in our senior executive positions on a timely basis could adversely affect our ability to implement our business strategy, which would negatively impact our results of operations.

Terrorism and the uncertainty of war may have a material adverse effect on our operating results.

Terrorist attacks, such as the attacks that occurred in New York and Washington, D.C. on September 11, 2001, and other acts of violence or war may affect the operations of the United States securities markets, the markets in which we operate and our operations and profitability. Further terrorist attacks against the United States or U.S. businesses may occur. The potential near-term and long-term effect these attacks may have for our customers, the markets for our services and the U.S. economy are uncertain. The consequences of any terrorist attacks, or any armed conflicts which may result, are unpredictable, and we may not be able to foresee events that could have an adverse effect on our business or your investment.

Concentration of ownership among our existing executive officers, directors and principal stockholders may prevent new investors from influencing significant corporate decisions.

Upon completion of this offering, our executive officers, directors and principal stockholders will own, in the aggregate, approximately 51.5% of our outstanding common stock. As a result, these stockholders will have significant influence over all matters requiring stockholder approval, including the election of directors, amendment of our certificate of incorporation and approval of significant corporate transactions, and will otherwise have significant influence over our management and policies. The directors elected by these stockholders will be able to make decisions affecting our capital structure, including decisions to issue additional capital stock, implement stock repurchase programs and incur indebtedness. Green Equity Investors III, L.P. and TPG Partners III, L.P. and its affiliates are parties to an agreement, pursuant to which they agreed to vote for two nominees of Green Equity Investors III, L.P. and two nominees of TPG Partners III, L.P. and its affiliates. This concentration of ownership may have the effect of deterring hostile takeovers, delaying or preventing changes in control or changes in management, or limiting the ability of our other stockholders to approve transactions that they may deem to be in their best interests.

Future sales of shares of our common stock in the public market may depress our stock price and make it difficult for you to recover the full value of your investment in our shares.

If our existing stockholders sell substantial amounts of our common stock in the public market or if there is a perception that these sales may occur, the market price of our common stock could decline. As of June 13, 2003, we had and, assuming no exercise of outstanding options to purchase common stock, immediately following this offering we will have 57,408,767 shares of common stock outstanding. Of these shares, the 1,880,000 shares of common stock to be sold in this offering, the 10,350,000 shares of common stock sold in our recently completed public offering, which we refer to as the prior offering, the 16,675,000 shares of common stock sold in our initial public offering and the shares sold to date by our stockholders pursuant to Rules 144, 144(k) or 701 under the Securities Act of 1933, as amended, will be freely tradable in the public market without restriction or further registration under the Securities Act, unless the shares are held by "affiliates" of ours as such term is defined in Rule 144 of the Securities Act.

We also have 3,114,901 shares of common stock reserved for issuance under our stock option and incentive plans, of which 2,235,586 shares were subject to outstanding options as of June 13, 2003. In March 2002, we filed a registration statement on Form S-8 to register all of the shares of common stock which could be purchased upon the exercise of stock options outstanding on that date and all other shares of common stock reserved for future issuance under our stock option and incentive plans. Accordingly, shares issued upon exercise of such options are freely tradable by holders who are not our affiliates and, subject to the volume and other limitations of Rule 144, by holders who are affiliates.

All remaining shares held by our existing stockholders were issued and sold by us in private transactions, or are shares retained by senior management in connection with our recapitalization

transaction in October 2000, and are eligible for public sale if registered under the Securities Act or sold in accordance with Rules 144, 144(k) or 701 thereunder, except for 24,339,953 shares beneficially owned by our executive officers, directors and the selling stockholders, which are subject to lock-up agreements entered into in connection with the prior offering pursuant to which these individuals have agreed not to offer or sell any of these shares of common stock for a period of 90 days from May 22, 2003 without the prior written consent of Goldman, Sachs & Co. and Morgan Stanley & Co. Incorporated, on behalf of the underwriters. The sale of a substantial number of shares of our common stock following the expiration of the lock-up period could cause our stock price to fall.

Since our initial public offering in February 2002, the price at which our common stock has traded has been subject to significant fluctuation. The market price for our common stock in the future may continue to be volatile. In addition, the stock market has recently experienced significant price and volume fluctuations that in many instances have been unrelated or disproportionate to the operating performance of specific companies. In the past, following periods of volatility in the market price of a particular company's securities, securities class-action litigation has often been brought against that company. If similar litigation were instituted against us, it could result in substantial costs and divert management's attention and resources from our core business.

Our stock price may be adversely affected because our results of operations may fluctuate from quarter to quarter.

The timing of new store openings, related pre-opening expenses and the amount of revenue contributed by new and existing stores may cause our quarterly results of operations to fluctuate. Our business is also subject to seasonal fluctuation. Historically, we have realized a higher portion of our net sales during the month of December than during the other months of the year. If our quarterly revenue and operating results fall below the expectations of securities analysts and investors, the market price of our common stock could fall substantially.

Operating results also may vary depending on a number of factors, many of which are outside our control, including:

Takeover defense provisions may adversely affect the market price of our common stock.

Various provisions of the Delaware general corporation law, or the DGCL, and of our corporate governance documents may inhibit changes in control not approved by our board of directors and may have the effect of depriving you of an opportunity to receive a premium over the prevailing market price of our common stock in the event of an attempted hostile takeover. In addition, the existence of these provisions may adversely affect the market price of our common stock. These provisions include:

Some of the statements under "Prospectus Supplement Summary," "Risk Factors" and elsewhere in this prospectus supplement, the accompanying prospectus and the information incorporated by reference are forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Securities Exchange Act of 1934, as amended. These statements are therefore entitled to the protection of the safe harbor provisions of these laws. We generally identify forward-looking statements in this prospectus supplement, the accompanying prospectus and the information incorporated by reference using words like "believe," "intend," "target," "expect," "estimate," "may," "should," "plan," "project," "contemplate," "anticipate," "predict" or similar expressions. You can also identify forward-looking statements by discussions of strategy, plans or intentions. These statements involve known and unknown risks, uncertainties and other factors, including those described in the "Risk Factors" section of this prospectus supplement, that may cause our or our industry's actual results, levels of activity, performance or achievements to be materially different from any future results, levels of activity, performance or achievements expressed or implied by these forward-looking statements. Except as required by applicable law, including the securities laws of the United States, and the rules and regulations of the Securities and Exchange Commission, we do not plan to publicly update or revise any forward-looking statements after we distribute this prospectus supplement, whether as a result of any new information, future events or otherwise.

All of the shares of common stock offered by this prospectus supplement are being sold by the selling stockholders. We will not receive any proceeds from this offering.

We have not paid cash dividends on our common stock. We currently intend to retain all future earnings, if any, for use in the operation of our business and we do not anticipate paying cash dividends in the foreseeable future. In addition, our senior credit facility and the indenture governing our senior subordinated notes place limitations on our ability to pay dividends or make other distributions in respect of our common stock. Any future determination as to the payment of dividends on our common stock will be restricted by these limitations, will be at the discretion of our board of directors and will depend on our results of operations, financial condition, capital requirements and other factors deemed relevant by the board of directors, including the DGCL, which provides that dividends are only payable out of surplus or current net profits.

Our common stock has been listed on The Nasdaq Stock Market's National Market under the symbol "PETC" since it was initially offered to the public on February 22, 2002. Prior to that time, there had not been a market for our common stock. The following table shows the high and low per share sale prices of our common stock, as reported on the Nasdaq National Market for the periods indicated:

	High		Low
Fiscal Year—2002
First Quarter (commencing February 22, 2002)	$	25.75	$	19.00
Second Quarter	$	26.70	$	16.55
Third Quarter	$	25.20	$	16.31
Fourth Quarter	$	25.95	$	20.57
Fiscal Year—2003
First Quarter	$	21.72	$	15.20
Second Quarter (through June 20, 2003)	$	22.55	$	18.92

On June 20, 2003, the last reported sale price of our common stock on the Nasdaq National Market was $22.36. As of June 20, 2003, there were approximately 100 holders of record of our common stock.

The following table sets forth information about the selling stockholders' beneficial ownership of our common stock as of June 13, 2003 (such information has been provided by the selling stockholders) and after the sale of the common stock offered by each selling stockholder. The numbers presented assume that all of the shares offered by the selling stockholders are sold and that the selling stockholders acquire no additional shares of our common stock before the completion of this offering. We will pay all expenses incurred with respect to the registration and sale of the shares of common stock owned by the selling stockholders, other than underwriting fees, discounts or commissions, which will be borne by the selling stockholders.

Beneficial ownership of shares is determined under the rules of the Securities and Exchange Commission and generally includes any shares over which a person exercises sole or shared voting or investment power. Each person identified in the table possesses sole voting and investment power with respect to all shares of common stock held by them, except as indicated by footnote or to the extent this power may be shared with a spouse. The percentage of outstanding shares beneficially owned is based on 57,408,767 shares of common stock outstanding as of June 13, 2003. Shares of common stock subject to options currently exercisable or exercisable within 60 days of June 13, 2003 are deemed outstanding for calculating the percentage of outstanding shares of the person holding these options, but are not deemed outstanding for calculating the percentage of any other person.

		Shares of Common Stock Beneficially Owned Before the Offering				Shares of Common Stock Beneficially Owned After the Offering
		Shares of Common Stock to be Sold in the Offering
Name of Selling Stockholder
	Number		Percentage		Number		Percentage
Green Equity Investors III, L.P.(1)(2)		10,220,954		17.8	%	940,000		9,280,954	16.2	%
TPG Partners III, L.P.(1)(3)		7,730,726		13.5		710,979		7,019,747	12.2
TPG Parallel III, L.P.(1)(3)		1,486,434		2.6		136,704		1,349,730	2.4
TPG Dutch Parallel III, C.V.(1)(3)		491,854		*		45,235		446,619	*
FOF Partners III-B, L.P.(1)(3)		285,777		*		26,282		259,495	*
TPG Investors III, L.P.(1)(3)		213,306		*		19,617		193,689	*
FOF Partners III, L.P.(1)(3)		12,858		*		1,183		11,675	*

In October 2000, we completed a leveraged recapitalization with an entity controlled by Leonard Green & Partners, L.P. and its affiliates, which we refer to collectively as Leonard Green, and TPG Partners III, L.P. and its affiliates, which we refer to collectively as Texas Pacific Group. Green Equity Investors III, L.P. is an affiliate of Leonard Green and TPG Partners III, L.P., TPG Parallel III, L.P.,

TPG Dutch Parallel III, C.V., TPG Investors III, L.P., FOF Partners III, L.P. and FOF Partners III-B, L.P. are affiliates of Texas Pacific Group.

In connection with the recapitalization transaction, we entered into a ten year management services agreement with Leonard Green and Texas Pacific Group, who acted as the managers under the agreement. Under the management services agreement, the managers provided management, consulting and financial planning services and transaction-related financial advisory and investment banking services to us and our subsidiaries. We paid a one-time structuring fee of $8.0 million to the managers in October 2000 under the agreement. The managers received an annual fee of approximately $3.1 million as compensation for the general services they provided under the management services agreement and normal and customary fees for transaction-related services, and were reimbursed for out-of-pocket expenses. Shortly after the closing of our initial public offering in February 2002, we paid Leonard Green and Texas Pacific Group an aggregate amount of approximately $12.5 million to terminate the management services agreement.

In connection with the recapitalization transaction, we also entered into a stockholders agreement with certain of our stockholders, including Leonard Green and Texas Pacific Group. The stockholders agreement was amended and restated in connection with our initial public offering in February 2002. Under the amended and restated stockholders agreement, certain of our stockholders, including Leonard Green and Texas Pacific Group, may demand that we file a registration statement under the Securities Act covering some or all of the stockholder's registrable securities. In addition, if we propose to register any of our equity securities under the Securities Act, other than in connection with a demand registration or other excluded registration, the stockholders may require that we include all or a portion of their registrable securities in the registration and in any related underwriting. In an underwritten offering, the managing underwriter, if any, has the right, subject to specified conditions, to limit the number of registrable securities. In general, we will bear all fees, costs and expenses of registrations under the stockholders agreement, other than underwriting discounts and commissions. The parties to the stockholders agreement, including the selling stockholders, have waived any registration rights they may have in connection with any sale of common stock pursuant to this prospectus supplement or any other prospectus supplement relating to the accompanying prospectus.

John M. Baumer, Jonathan Coslet, John G. Danhakl and William S. Price III each serve on our board of directors. Messrs. Baumer and Danhakl are partners of Leonard Green & Partners, L.P. Messrs. Coslet and Price are partners of Texas Pacific Group.

The following summary describes the material United States federal income tax consequences of the ownership of common stock by a non-U.S. holder as of the date hereof. This discussion does not address all aspects of United States federal income taxes that may be relevant to a non-U.S. holder of common stock. For example, in the case of a non-U.S. holder that is a partnership, the United States tax consequences of holding and disposing of our common stock may be affected by determinations made at the partner level. This discussion also does not address foreign, state and local tax consequences. Special rules may apply to certain non-U.S. holders, such as insurance companies, tax-exempt organizations, banks, financial institutions, dealers in securities, holders of securities held as part of a "straddle," "hedge" or "conversion transaction," "controlled foreign corporations," "passive foreign investment companies," "foreign personal holding companies" and corporations that accumulate earnings to avoid United States federal income tax, that are subject to special treatment under the Internal Revenue Code of 1986, as amended, or the Code. Such persons should consult their own tax advisors to determine the United States federal, state, local and other tax consequences that may be relevant to them. Furthermore, the discussion below is based upon the provisions of the Code, and regulations, rulings and judicial decisions thereunder as of the date hereof, and these authorities may be repealed, revoked or modified with retroactive effect so as to result in United States federal income tax consequences different from those discussed below.

Persons considering the purchase, ownership or disposition of common stock should consult their own tax advisors concerning the United States federal income tax consequences in light of their particular situations as well as any consequences arising under the laws of any other taxing jurisdiction.

As used in this section, a "U.S. holder" of common stock means a holder that is (1) a citizen or resident of the United States, (2) a corporation or partnership created or organized in or under the laws of the United States or of any state thereof or in the District of Columbia, unless in the case of a partnership, United States Treasury regulations provide otherwise, (3) an estate the income of which is subject to United States federal income taxation regardless of its source and (4) a trust (A) if a court within the United States is able to exercise primary supervision over the administration of the trust and one or more United States persons has the authority to control all substantial decisions of the trust or (B) that has a valid election in effect under applicable United States Treasury regulations to be treated as a United States person. A "non-U.S. holder" is a holder that is not a U.S. holder.

Dividends paid to a non-U.S. holder of common stock generally will be subject to withholding of United States federal income tax at a 30% rate or such lower rate as may be specified by an applicable income tax treaty. However, dividends that are effectively connected with the conduct of a trade or business by the non-U.S. holder within the United States and, where a tax treaty applies, are attributable to a United States permanent establishment of the non-U.S. holder, are not subject to withholding tax, but instead are subject to United States federal income tax on a net income basis at applicable graduated individual or corporate rates. Certain certification and disclosure requirements must be complied with in order for effectively connected income to be exempt from withholding. Any such effectively connected dividends received by a foreign corporation may be subject to an additional "branch profits tax" at a 30% rate or such lower rate as may be specified by an applicable income tax treaty. A non-U.S. holder of common stock who wishes to claim the benefit of an applicable treaty rate (and avoid back-up withholding as discussed below) for dividends paid will be required to satisfy applicable certification and other requirements and may be required to obtain a United States taxpayer identification number.

A non-U.S. holder of common stock eligible for a reduced rate of United States withholding tax may obtain a refund of any excess amounts withheld by filing an appropriate claim for refund with the Internal Revenue Service, or the IRS.

A non-U.S. holder generally will not be subject to United States federal income tax with respect to gain recognized on a sale or other disposition of common stock unless (1) the gain is effectively connected with a trade or business of the non-U.S. holder in the United States, and, where a tax treaty applies, is attributable to a United States permanent establishment of the non-U.S. holder, (2) in the case of a non-U.S. holder who is an individual and holds the common stock as a capital asset, such holder is present in the United States for 183 or more days in the taxable year of the sale or other disposition and certain other conditions are met or (3) we are or have been a "U.S. real property holding corporation" for United States federal income tax purposes.

A non-U.S. holder described in clause (1) above will be subject to tax on the net gain derived from the sale under regular graduated United States federal income tax rates and, if it is a corporation, may be subject to the branch profits tax at a rate equal to 30% of its effectively connected earnings and profits or at such lower rate as may be specified by an applicable income tax treaty. An individual non-U.S. holder described in clause (2) above will be subject to a flat 30% tax on the gain derived from the sale, which may be offset by United States source capital losses (even though the individual is not considered a resident of the United States).

We believe we are not and do not anticipate becoming a "U.S. real property holding corporation" for United States federal income tax purposes.

We must report annually to the IRS and to each non-U.S. holder the amount of dividends paid to such holder and the tax withheld with respect to such dividends, regardless of whether withholding was required. Copies of the information returns reporting such dividends and withholding may also be made available to the tax authorities in the country in which the non-U.S. holder resides under the provisions of an applicable income tax treaty.

A non-U.S. holder may be subject to back-up withholding unless applicable certification requirements are met.

Payment of the proceeds of a sale of common stock within the United States is subject to both backup withholding and information reporting unless the beneficial owner certifies under penalties of perjury that it is a non-U.S. holder (and the payor does not have actual knowledge or reason to know that the beneficial owner is a United States person) or the holder otherwise establishes an exemption. Payment of the proceeds of a sale of common stock conducted through certain United States related financial intermediaries is subject to information reporting (but not backup withholding) unless the financial intermediary has documentary evidence in its records that the beneficial owner is a non-U.S. holder and specified conditions are met or an exemption is otherwise established.

Any amounts withheld under the backup withholding rules may be allowed as a refund or a credit against such holder's United States federal income tax liability provided the required information is furnished to the IRS.

All of the shares of common stock offered hereby are being sold by the selling stockholders named in this prospectus supplement directly to a group of related institutional investors. No underwriting fees or commissions will be paid in connection with the offering. We may from time to time engage in financing transactions, including public offerings and private placements of equity securities.

The validity of the common stock offered hereby will be passed upon for us by Latham & Watkins LLP, San Diego, California.

The consolidated financial statements of PETCO Animal Supplies as of February 2, 2002 and February 1, 2003, and for each of the years in the three year period ended February 1, 2003 have been incorporated by reference herein in reliance upon the report of KPMG LLP, independent accountants, and upon the authority of said firm as experts in accounting and auditing. The audit report covering the year ended February 1, 2003 refers to a change in accounting for goodwill.

We may offer and sell from time to time shares of common stock in amounts, at prices and on the terms that we will determine at the time of offering, with an aggregate initial offering price of up to $55,000,000. In addition, the selling stockholders named in this prospectus may sell up to 11,500,000 shares of our common stock. We will not receive any of the proceeds from the sale of our common stock by the selling stockholders.

We will provide the specific terms of these offers and sales in supplements to this prospectus. You should read this prospectus and any supplements carefully before you invest. We and the selling stockholders may sell common stock directly to purchasers or through agents or through underwriters or dealers as designated from time to time. If any agents, underwriters or dealers are involved in the sale of the common stock, the applicable prospectus supplement will provide the names of the agents, underwriters or dealers and any applicable fees, commissions or discounts.

Our common stock is listed on the Nasdaq National Market under the symbol "PETC."

Investing in our securities involves risks, which we describe in our Annual Report on Form 10-K and in other documents that we subsequently file with the Securities and Exchange Commission, and which we will describe in supplements to this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

You should rely only on the information contained or incorporated by reference in this prospectus. We have not authorized anyone to provide you with different information. We are not making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should not assume that the information contained in this prospectus is accurate as of any date other than the date on the front of this prospectus.

		Page
About this Prospectus		3
Where You Can Find More Information		3
Cautionary Note Regarding Forward-Looking Statements		4
PETCO		5
Use of Proceeds		5
Selling Stockholders		6
Plan of Distribution		8
Description of Capital Stock		10
Legal Matters		11
Experts		11

Whenever we refer to "PETCO," "we," "our" or "us" in this prospectus, we mean PETCO Animal Supplies, Inc. and its consolidated subsidiaries, unless the context suggests otherwise.

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission using a "shelf" registration process. Under this shelf registration process, we may sell common stock from time to time in one or more offerings up to a total dollar amount of $55,000,000. Certain selling stockholders referred to in this prospectus and identified in supplements to this prospectus may also offer and sell shares of our common stock under this prospectus. We will not receive any of the proceeds from any sales of shares by the selling stockholders. Each time we offer to sell or a selling stockholder offers to sell securities under this prospectus, we will provide a prospectus supplement that will contain specific information about the terms of that offering. The prospectus supplement may also add, update or change information contained in this prospectus. To the extent that any statement that we make in a prospectus supplement is inconsistent with statements made in this prospectus, the statements made in this prospectus will be deemed modified or superseded by those made in a prospectus supplement. You should read both this prospectus and any prospectus supplement together with additional information described under the next heading, "Where You Can Find More Information."

We are subject to the reporting and information requirements of the Securities Exchange Act of 1934, as amended, and, as a result, file periodic reports, proxy statements and other information with the SEC. You may read and copy these periodic reports, proxy statements and other information at the public reference facilities maintained by the SEC in Room 1024, 450 Fifth Street, N.W., Washington, D.C. 20549. Information on the operation of the public reference facilities may be obtained by calling the SEC at 1-800-SEC-0330. The SEC maintains a World Wide Web site that contains reports, proxy and information statements and other information regarding registrants like us that file electronically with the SEC. The address of the site is http://www.sec.gov.

We are incorporating by reference some information about us that we file with the SEC. We are disclosing important information to you by referencing those filed documents. Any information that we reference this way is considered part of this prospectus. The information in this prospectus supersedes information incorporated by reference that we have filed with the SEC prior to the date of this prospectus, while information that we file with the SEC after the date of this prospectus that is incorporated by reference will automatically update and supersede this information.

We incorporate by reference the following documents we have filed, or may file, with the SEC:

You may request a free copy of any of the documents incorporated by reference in this prospectus by writing or telephoning us at the following address:

PETCO Animal Supplies, Inc.
Attention: Investor Relations
9125 Rehco Road
San Diego, California 92121
(858) 453-7845

This prospectus contains and incorporates by reference forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Exchange Act. These statements are therefore entitled to the protection of the safe harbor provisions of these laws. We generally identify forward-looking statements in this prospectus using words like "believe," "intend," "target," "expect," "estimate," "may," "should," "plan," "project," "contemplate," "anticipate," "predict" or similar expressions. You can also identify forward-looking statements by discussions of strategy, plans or intentions. These statements involve known and unknown risks, uncertainties and other factors, including those detailed in our Annual Report on Form 10-K under the heading "Certain Cautionary Statements," that may cause our or our industry's actual results, levels of activity, performance or achievements to be materially different from any future results, levels of activity, performance or achievements expressed or implied by these forward-looking statements. Except as required by applicable law, including the securities laws of the United States, and the rules and regulations of the SEC, we do not plan to publicly update or revise any forward-looking statements after we distribute this prospectus, whether as a result of any new information, future events or otherwise.

We are a leading specialty retailer of premium pet food, supplies and services with 600 stores in 43 states and the District of Columbia. Our products include pet food, supplies, grooming products, toys, novelty items and vitamins, small pets such as fish, birds and other small animals (excluding cats and dogs), and veterinary supplies. Our strategy is to offer our customers a complete assortment of pet-related products and services at competitive prices, with superior levels of customer service at convenient locations.

Unless otherwise indicated in a prospectus supplement, we currently intend to use the net proceeds from our sale of common stock to redeem up to $40.0 million in principal amount of our outstanding 10.75% senior subordinated notes due 2011. Under the indenture governing the senior subordinated notes, we would be required to pay a 10.75% redemption premium and accrued and unpaid interest through the date of redemption in order to redeem the senior subordinated notes. Alternatively, we may elect to purchase indebtedness, in open market purchases, negotiated transactions or otherwise, with the net proceeds from our sale of common stock. We currently intend to use any remaining net proceeds for general corporate purposes. Pending these uses, the net proceeds will be invested in investment-grade, interest-bearing securities.

We will not receive any of the proceeds from the sale of our common stock by the selling stockholders.

The following table sets forth information about the selling stockholders' beneficial ownership of our common stock as of March 19, 2003 (such information has been provided by the selling stockholders) and after the sale of the common stock offered by each selling stockholder, assuming all such shares are sold. None of the selling stockholders has committed to sell any shares under this prospectus. The percentage of outstanding shares beneficially owned is based on 57,373,067 shares of common stock outstanding as of March 19, 2003. The numbers presented under "Shares of Common Stock Beneficially Owned After the Offering" assume that all of the shares offered by the selling stockholders are sold and that the selling stockholders acquire no additional shares of our common stock before the completion of this offering. The selling stockholders may offer all, some or none of the shares of our common stock beneficially owned by them. We will pay all expenses incurred with respect to the registration and sale of the shares of common stock owned by the selling stockholders, other than underwriting fees, discounts or commissions, which will be borne by the selling stockholders. The shares offered by this prospectus may be offered from time to time by the selling stockholders named below.

The term "selling stockholders," as used in this prospectus, includes the persons listed below and any transferees, pledgees, donees, heirs or other successors receiving shares from the persons listed below after the date of this prospectus.

		Shares of Common Stock Beneficially Owned Before the Offering		Shares of Common Stock To Be Sold In the Offering		Shares of Common Stock Beneficially Owned After the Offering
Name of Selling Stockholder
	Number		Percentage		Number		Percentage
Green Equity Investors III, L.P.(1)(2)		15,030,954		26.2	%	5,750,000		9,280,954	16.2	%
TPG Partners III, L.P.(1)(3)		11,368,813		19.8		4,349,070		7,019,743	12.2
TPG Parallel III, L.P.(1)(3)		2,185,952		3.8		836,223		1,349,729	2.4
TPG Dutch Parallel III, C.V.(1)(3)		723,320		1.3		276,702		446,618	*
FOF Partners III-B, L.P.(1)(3)		420,265		*		160,770		259,495	*
TPG Investors III, L.P.(1)(3)		313,696		*		120,002		193,694	*
FOF Partners III, L.P.(1)(3)		18,909		*		7,233		11,676	*

In connection with the recapitalization transaction, we also entered into a stockholders agreement with certain of our stockholders, including the selling stockholders. The stockholders agreement was amended and restated in connection with our initial public offering in February 2002. Under the amended and restated stockholders agreement, certain of our stockholders, including the selling stockholders, may demand that we file a registration statement under the Securities Act covering some or all of the stockholder's registrable securities. In addition, if we propose to register any of our equity securities under the Securities Act, other than in connection with a demand registration or other excluded registration, the stockholders may require that we include all or a portion of their registrable securities in the registration and in any related underwriting. In an underwritten offering, the managing underwriter, if any, has the right, subject to specified conditions, to limit the number of registrable securities. In general, we will bear all fees, costs and expenses of registrations under the stockholders agreement, other than underwriting discounts and commissions. The selling stockholders have waived any registration rights they may have in connection with any sale of common stock pursuant to this prospectus or any prospectus supplement.

John M. Baumer, Jonathan Coslet, John G. Danhakl and William S. Price III each serve on our board of directors. Messrs. Baumer and Danhakl are partners of Leonard Green & Partners, L.P. Mr. Coslet is an executive of Texas Pacific Group and Mr. Price is a founding partner of Texas Pacific Group.

We and the selling stockholders currently intend to offer and sell the common stock in one or more underwritten public offerings. However, we and/or any selling stockholders may also offer and sell shares of common stock:

The distribution of the common stock may be effected from time to time in one or more transactions either:

Offers to purchase the common stock may be solicited by agents designated by us and/or any selling stockholders from time to time. Any agent involved in the offer or sale of the common stock will be named, and any commissions payable by us and/or any selling stockholders to the agent will be described, in the applicable prospectus supplement. Unless otherwise indicated in the applicable prospectus supplement, any such agent will be acting on a best efforts basis for the period of its appointment. Any agent may be deemed to be an underwriter, as such term is defined in the Securities Act, of the common stock so offered and sold.

If we and/or any selling stockholders offer and sell common stock through an underwriter or underwriters, we and/or the selling stockholders will execute an underwriting agreement with the underwriter or underwriters. The names of the specific managing underwriter or underwriters, as well as any other underwriters, and the terms of the transactions, including compensation of the underwriters and dealers, which may be in the form of discounts, concessions or commissions, if any, will be described in the applicable prospectus supplement, which will be used by the underwriters to make resales of the common stock. That prospectus supplement and this prospectus will be used by the underwriters to make resales of the common stock. If underwriters are used in the sale of any common stock in connection with this prospectus, those shares of common stock will be acquired by the underwriters for their own account and may be resold from time to time in one or more transactions, including negotiated transactions, at fixed public offering prices or at varying prices determined by the underwriters and us and/or any selling stockholders at the time of sale. Shares of common stock may be offered to the public either through underwriting syndicates represented by managing underwriters or directly by one or more underwriters. If any underwriter or underwriters are used in the sale of common stock, unless otherwise indicated in a related prospectus supplement, the underwriting agreement will provide that the obligations of the underwriters are subject to some conditions precedent and that with respect to a sale of those shares of common stock the underwriters will be obligated to purchase all such securities if any are purchased.

If any underwriters are involved in the offer and sale, they will be permitted to engage in transactions that maintain or otherwise affect the price of the common stock. These transactions may include over-allotment transactions, purchases to cover short positions created by the underwriter in

connection with the offering and the imposition of penalty bids. If an underwriter creates a short position in the common stock in connection with the offering, i.e., if it sells more shares of common stock than set forth on the cover page of the applicable prospectus supplement, the underwriter may reduce that short position by purchasing common stock in the open market. In general, purchases of common stock to reduce a short position could cause the price of the common stock to be higher than it might be in the absence of such purchases. As noted above, underwriters may also choose to impose penalty bids on other underwriters and/or selling group members. This means that if underwriters purchase common stock on the open market to reduce their short position or to stabilize the price of the common stock, they may reclaim the amount of the selling concession from those underwriters and/or selling group members who sold such common stock as part of the offering.

If we and/or the selling stockholders offer and sell common stock through a dealer, we, the selling stockholders or an underwriter will sell the common stock to the dealer, as principal. The dealer may then resell the common stock to the public at varying prices to be determined by the dealer at the time of resale. Any such dealer may be deemed to be an underwriter, as such term is defined in the Securities Act, of the common stock so offered and sold. The name of the dealer and the terms of the transactions will be set forth in the applicable prospectus supplement.

We and/or the selling stockholders may solicit offers to purchase the common stock directly and we and/or the selling stockholders may sell the common stock directly to institutional or other investors, who may be deemed to be an underwriter within the meaning of the Securities Act with respect to any resales of those shares of common stock. The terms of these sales, including the terms of any bidding or auction process, if utilized, will be described in the applicable prospectus supplement.

We and/or the selling stockholders may enter into agreements with agents, underwriters and dealers under which we and/or the selling stockholders may agree to indemnify the agents, underwriters and dealers against certain liabilities, including liabilities under the Securities Act, or to contribute to payments they may be required to make with respect to these liabilities. The terms and conditions of this indemnification or contribution will be described in the applicable prospectus supplement. Some of the agents, underwriters or dealers, or their affiliates may be customers of, engage in transactions with or perform services for us and/or the selling stockholders in the ordinary course of business.

We and/or the selling stockholders may authorize our respective agents or underwriters to solicit offers to purchase common stock at the public offering price under delayed delivery contracts. The terms of these delayed delivery contracts, including when payment for and delivery of the common stock sold will be made under the contracts and any conditions to each party's performance set forth in the contracts, will be described in the applicable prospectus supplement. The compensation received by underwriters or agents soliciting purchases of common stock under delayed delivery contracts will also be described in the applicable prospectus supplement.

From time to time, one or more of the selling stockholders may pledge or grant a security interest in some or all of our shares of common stock owned by them. If the selling stockholders default in the performance of their secured obligations, the pledgees or secured parties may offer and sell such common stock from time to time by this prospectus. The selling stockholders also may transfer and donate our common stock owned by them in other circumstances. The number of shares of our common stock beneficially owned by selling stockholders will decrease as and when the selling stockholders transfer or donate their shares of our common stock or default in performing obligations secured by their shares of our common stock. The plan of distribution for the securities offered and sold under this prospectus will otherwise remain unchanged, except that the transferees, donees, pledgees, other secured parties or other successors in interest will be selling stockholders for purposes of this prospectus.

This prospectus contains a summary of the material terms of our capital stock. The following description of our capital stock is subject to, and qualified in its entirety by, our certificate of incorporation and bylaws, which are included as exhibits to the registration statement of which this prospectus forms a part, and by the provisions of applicable Delaware law.

Our authorized capital stock consists of 250,000,000 shares of common stock, par value $0.001 per share, and 5,000,000 shares of preferred stock, par value $0.01 per share.

As of March 19, 2003, there were 57,373,067 shares of common stock outstanding, held of record by approximately 100 stockholders. Holders of shares of our common stock are entitled to one vote per share on matters to be voted upon by the stockholders and, subject to the prior rights of the holders of preferred stock, to receive dividends when and as declared by the board of directors with funds legally available therefor and to share ratably in our assets legally available for distribution to the stockholders in the event of liquidation or dissolution, after payment of all debts and other liabilities. Holders of our common stock are not entitled to preemptive rights and have no subscription, redemption or conversion privileges. Our common stock does not have cumulative voting rights, which means the holder or holders of more than one-half of the shares voting for the election of directors can elect all of the directors then being elected. All of the outstanding shares of our common stock are fully paid and nonassessable. The rights, preferences and privileges of holders of our common stock are subject to the rights of the holders of shares of any series of preferred stock which we may issue in the future.

Our certificate of incorporation provides that our board of directors has the authority, without further action by the stockholders, to issue up to 5,000,000 shares of preferred stock, par value $0.01 per share, in one or more series and to fix the powers, preferences, privileges, rights and qualifications, limitations or restrictions thereof, including dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of the series, without any further vote or action by stockholders. We believe that the board of directors' authority to set the terms of, and our ability to issue, preferred stock will provide flexibility in connection with possible financing transactions in the future. The issuance of preferred stock, however, could adversely affect the voting power of holders of common stock, and the likelihood that the holders will receive dividend payments and payments upon liquidation could have the effect of delaying, deferring or preventing a change in control. We have no outstanding shares of preferred stock and no present plan to issue any shares of preferred stock.

Anti-takeover Provisions of our Charter, Bylaws and Delaware General Corporation Law

Stockholder Action; Advance Notification of Stockholder Nominations and Proposals. Our certificate of incorporation requires that any action required or permitted to be taken by our stockholders must be effected at a duly called annual or special meeting of stockholders and may not be effected by a consent in writing. Our certificate of incorporation also requires that special meetings of stockholders be called only by our board of directors, our chairman or our president. In addition, our bylaws provide that candidates for director may be nominated and other business brought before an annual meeting only by the board of directors or by a stockholder who gives written notice to us no later than 90 days prior nor earlier than 120 days prior to the first anniversary of the last annual meeting of stockholders. These provisions may have the effect of deterring hostile takeovers or delaying changes in control of our management, which could depress the market price of our common stock.

Number, Election and Removal of the Board of Directors. Our certificate of incorporation provides that the authorized number of directors will be as set forth in the bylaws and may be changed only by an amendment to the bylaws duly adopted by the board of directors or our stockholders. Our bylaws provide that the board of directors may consist of between five and fifteen members, with the actual number to be determined from time to time by resolution of the board of directors. Our board of

directors currently consists of nine members divided into three different classes. As a result, only one class of directors will be elected at each annual meeting of our stockholders, with the other classes continuing for the remainder of their respective terms. Between stockholder meetings, directors may be removed by our stockholders only for cause, and the board of directors may appoint new directors to fill vacancies or newly created directorships. These provisions may deter a stockholder from removing incumbent directors and from simultaneously gaining control of the board of directors by filling the vacancies created by removal with its own nominees.

Delaware Anti-Takeover Law. We are subject to Section 203 of the Delaware General Corporation Law, or the DGCL. In general, Section 203 prohibits a publicly held Delaware corporation from engaging in a "business combination" with an "interested stockholder" for a period of three years following the date the person became an interested stockholder, unless the "business combination" or the transaction in which the person became an interested stockholder is approved in a prescribed manner. Generally, a "business combination" includes a merger, asset or stock sale, or other transaction resulting in a financial benefit to the interested stockholder. Generally, an "interested stockholder" is a person who, together with affiliates and associates, owns or within three years prior to the determination of interested stockholder status, did own, 15% or more of a corporation's voting stock. The existence of this provision may have an anti-takeover effect with respect to transactions not approved in advance by our board of directors, including discouraging attempts that might result in a premium over the market price for the shares of common stock held by stockholders.

Our certificate of incorporation and bylaws allow us to eliminate the personal liability of our directors and to indemnify directors and officers to the fullest extent permitted by the DGCL.

We have also entered into indemnity agreements with each of our directors and officers, which provide for mandatory indemnity of an officer or director made party to a "proceeding" by reason of the fact that he or she is or was an officer or director of ours, if he or she acted in good faith and in a manner he or she reasonably believed to be in or not opposed to our best interests. These agreements also obligate us to advance expenses to an indemnitee provided that he or she agrees to repay advanced expenses in the event he or she is not entitled to indemnification. Indemnitees are also entitled to partial indemnification, and indemnification for expenses incurred as a result of acting at our request as a director, officer or agent of an employee benefit plan or other partnership, corporation, joint venture, trust or other enterprise owned or controlled by us.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to our directors, officers and controlling persons pursuant to the above provisions or otherwise, we have been advised that, in the opinion of the SEC, such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable.

The transfer agent and registrar for our common stock is American Stock Transfer & Trust Company.

Our common stock is listed on the Nasdaq National Market under the symbol "PETC."

The validity of the common stock offered hereby will be passed upon for us by Latham & Watkins LLP, San Diego, California.

Common stock offered by the selling stockholders		1,880,000 shares
Common stock to be outstanding immediately after this offering		57,408,767 shares
Use of proceeds		We will not receive any proceeds from this offering.
Nasdaq National Market symbol		"PETC"