AFFYMETRIX INC
S-3, 1997-10-17
COMMERCIAL PHYSICAL & BIOLOGICAL RESEARCH
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<PAGE>
   AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON OCTOBER 17, 1997.
                                                     REGISTRATION NO. 333-
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                               ------------------
                                    FORM S-3
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
                               ------------------
                                AFFYMETRIX, INC.
 
             (Exact name of registrant as specified in its charter)
 
<TABLE>
<S>                              <C>                            <C>
          CALIFORNIA                         8731                  77-0319159
 (State or other jurisdiction    (Primary Standard Industrial   (I.R.S. employer
              of                 Classification Code Number)     identification
incorporation or organization)                                      number)
</TABLE>
 
     3380 CENTRAL EXPRESSWAY, SANTA CLARA, CALIFORNIA 95051 (408) 731-5000
 
  (Address, including zip code, and telephone number, including area code, of
                   registrant's principal executive offices)
 
                               EDWARD M. HURWITZ
                                AFFYMETRIX, INC.
             3380 CENTRAL EXPRESSWAY, SANTA CLARA, CALIFORNIA 95051
                                 (408) 731-5000
 
 (Name, address, including zip code, and telephone number, including area code,
                             of agent for service)
                             ----------------------
 
           with copies of all orders, notices and communications to:
 
<TABLE>
<S>                                       <C>
           JULIAN N. STERN                          ALISON S. RESSLER
         STEPHEN C. FERRUOLO                       Sullivan & Cromwell
   Heller Ehrman White & McAuliffe               444 South Flower Street
        525 University Avenue                 Los Angeles, California 90071
     Palo Alto, California 94301                Telephone: (213) 955-8000
      Telephone: (650) 324-7000                 Facsimile: (213) 683-0457
      Facsimile: (650) 324-0638
</TABLE>
 
                             ----------------------
 
        APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:
   As soon as practicable after the Registration Statement becomes effective.
                             ----------------------
 
    If the only securities being registered on this Form are being offered
pursuant to dividend or interest reinvestment plans, please check the following
box. / /
 
    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 of
1933, other than securities offered only in connection with dividend or interest
reinvestment plans, 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
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 delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box. / /
                             ----------------------
 
                        CALCULATION OF REGISTRATION FEE
 
<TABLE>
<CAPTION>
                                                                       PROPOSED MAXIMUM     PROPOSED MAXIMUM
                TITLE OF SHARES                       AMOUNT TO       AGGREGATE OFFERING        AGGREGATE            AMOUNT OF
               TO BE REGISTERED                  BE REGISTERED(1)(2)   PRICE PER UNIT(3)    OFFERING PRICE(3)    REGISTRATION FEE
<S>                                              <C>                  <C>                  <C>                  <C>
Common Stock, no par value.....................       1,725,000             $42.75             $73,743,750            $22,347
</TABLE>
 
(1) Includes 225,000 shares of Common Stock that the Underwriters have the
    option to purchase to cover over-allotments, if any.
 
(2) In accordance with Rule 416 under the Securities Act of 1933, Common Stock
    offered hereby shall also be deemed to cover additional securities to be
    offered or issued to prevent dilution resulting from stock splits, stock
    dividends or similar transactions.
 
(3) Estimated solely for the purpose of computing the amount of the registration
    fee pursuant to Rule 457(c) under the Securities Act of 1933, as amended,
    based on the average of the high and low prices of the Common Stock on the
    Nasdaq National Market on October 16, 1997, as reported in THE WALL STREET
    JOURNAL. A portion of the proposed maximum aggregate offering price
    represents shares that are to be offered outside of the United States but
    that may be resold from time to time in the United States. Such shares are
    not being registered for the purpose of sales outside of the United States.
                             ----------------------
 
    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 THE REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(a),
MAY DETERMINE.
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>
INFORMATION CONTAINED HEREIN IS SUBJECT TO COMPLETION OR AMENDMENT. A
REGISTRATION STATEMENT RELATING TO THESE SECURITIES HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION. THESE SECURITIES MAY NOT BE SOLD NOR MAY
OFFERS TO BUY BE ACCEPTED PRIOR TO THE TIME THE REGISTRATION STATEMENT BECOMES
EFFECTIVE. THIS PROSPECTUS SHALL NOT CONSTITUTE AN OFFER TO SELL OR THE
SOLICITATION OF AN OFFER TO BUY NOR SHALL THERE BE ANY SALE OF THESE SECURITIES
IN ANY STATE IN WHICH SUCH OFFER, SOLICITATION OR SALE WOULD BE UNLAWFUL PRIOR
TO REGISTRATION OR QUALIFICATION UNDER THE SECURITIES LAWS OF ANY SUCH STATE.
<PAGE>
               SUBJECT TO COMPLETION, DATED                , 1997
 
                                1,500,000 SHARES
 
                                AFFYMETRIX, INC.
 
      [LOGO]
 
                                  COMMON STOCK
                                 (NO PAR VALUE)
 
                               ------------------
 
    Of the 1,500,000 shares of Common Stock offered, 1,200,000 shares are being
offered hereby in the United States and 300,000 shares are being offered in a
concurrent international offering outside the United States. The initial public
offering price and the aggregate underwriting discount per share will be
identical for both offerings. See "Underwriting."
 
    All of the shares of Common Stock offered hereby are being sold by the
Company.
 
    SEE "RISK FACTORS" BEGINNING ON PAGE 7 FOR CERTAIN CONSIDERATIONS RELEVANT
TO AN INVESTMENT IN THE COMMON STOCK.
 
    The last reported sale price of the Common Stock, which is quoted under the
symbol "AFFX", on the Nasdaq National Market on October 16, 1997 was $41.625 per
share. See "Price Range of Common Stock."
                               ------------------
 
THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
 EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE
   SECURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION
     PASSED UPON THE ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY
      REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.
                               ------------------
 
<TABLE>
<CAPTION>
                                                 INITIAL PUBLIC          UNDERWRITING            PROCEEDS TO
                                                 OFFERING PRICE           DISCOUNT(1)            COMPANY(2)
                                              ---------------------  ---------------------  ---------------------
<S>                                           <C>                    <C>                    <C>
Per Share...................................            $                      $                      $
Total(3)....................................            $                      $                      $
</TABLE>
 
- --------------
 
(1) The Company has agreed to indemnify the Underwriters against certain
    liabilities, including liabilities under the Securities Act of 1933. See
    "Underwriting."
 
(2) Before deducting estimated expenses of $500,000 payable by the Company.
 
(3) The Company has granted the U.S. Underwriters an option for 30 days to
    purchase up to an additional 180,000 shares at the initial public offering
    price per share, less the underwriting discount, solely to cover
    over-allotments. Additionally, the Company has granted the International
    Underwriters a similar option with respect to an additional 45,000 shares as
    a part of the concurrent international offering. If such options are
    exercised in full, the total initial public offering price, underwriting
    discount and proceeds to Company will be $         , $        and
    $         , respectively. See "Underwriting."
 
                               ------------------
 
    The shares offered hereby are offered severally by the U.S. Underwriters, as
specified herein, subject to receipt and acceptance by them and subject to their
right to reject any order in whole or in part. It is expected that certificates
for the shares will be ready for delivery in New York, New York, on or about
            , 1997 against payment therefor in immediately available funds.
 
GOLDMAN, SACHS & CO.
 
      BANCAMERICA ROBERTSON STEPHENS
 
            CREDIT SUISSE FIRST BOSTON
<PAGE>
                  NATIONSBANC MONTGOMERY SECURITIES, INC.
 
                               ------------------
 
               The date of this Prospectus is             , 1997.
<PAGE>
                                    GENOMICS
 
    Affymetrix intends to commercialize broadly the expression monitoring
applications of its GeneChip-Registered Trademark- probe array technology.
 
    Currently, the Company is offering custom and standard expression monitoring
probe arrays to its pharmaceutical, biotechnology, academic and clinical
reference laboratory customers.
 
    Affymetrix expects its customers to utilize the GeneChip probe arrays to
identify and validate novel targets for drug discovery. Customers include
Genetics Institute, Glaxo Wellcome, Hoechst, Merck, Parke-Davis, Pfizer and
Pioneer Hi-Bred. In August 1997, Roche became the Company's first EasyAccess-TM-
customer.
 
       [PICTURE OF THE GENECHIP-REGISTERED TRADEMARK- PROBE ARRAY CARTRIDGE.]
 
     [GRAPHICS OF PROBE ARRAY IMAGES SHOWING EXPRESSION PATTERNS OF NORMAL AND
                                 MALIGNANT CELL
LINES. GRAPHICAL REPRESENTATION OF IMAGES WITH QUANTITATIVE LEVELS OF EXPRESSION
                                  DISPLAYED.]
 
                               DISEASE MANAGEMENT
 
    Affymetrix intends to develop GeneChip-Registered Trademark- assays that
both monitor gene expression and resequence particular genes of interest to
improve human health care by enabling efficient and effective patient management
in infectious diseases, cancer and other areas, including correlation of genetic
variability to deficiencies in drug metabolism.
 
    Affymetrix has established partnerships and customer relationships with
leading diagnostic companies, clinical reference laboratories and medical
research centers to further its disease management strategy. These partnerships
and relationships include bioMerieux, Glaxo Wellcome and OncorMed.
 
    To date, Affymetrix has introduced two disease management GeneChip assays
for research only: the HIV and p53 GeneChip products. In both cases, Affymetrix
is working with clinical reference laboratories and commercial and academic
researchers to correlate specific mutations in these genes with therapeutic
outcomes.
 
    Diagnostic or disease management use of the Company's products would be
subject to FDA and other applicable regulatory approvals, which have not been
applied for or received, and which may not be obtained for several years, if at
all.
 
    [DEPICTION OF A GENECHIP PROBE ARRAY WITH ENLARGEMENT OF A FLUORESCENT IMAGE
  FOLLOWING HYBRIDIZATION, WITH GRAPHIC ILLUSTRATING IDENTICAL OLIGONUCLEOTIDE
                                     PROBES
                 CONTAINED IN ONE FEATURE OF THE PROBE ARRAY.]
 
                             POLYMORPHISM DISCOVERY
 
       [GRAPHIC OF THREE PEOPLE, THE GENECHIP PROBE ARRAY AND REPRESENTATIONS
                   OF THE BASE-CALLING HYBRIDIZATION IMAGE.]
 
       [GRAPHIC OF CHROMOSOMAL MAP INDICATING POSITION OF NOVEL POLYMORPHISM
                                   MARKERS.]
 
         [IMAGE OF FLUORESCENT SCAN OF PROBE ARRAY USED FOR GENOTYPING WITH
            GRAPHICAL ENLARGEMENT OF SELECTED PROBE ARRAY FEATURES.]
 
    As the identity of genes in the human genome is determined, the need to
understand the significance of the variability of the nucleotide sequences in
these genes increases. Researchers must determine the normal sequence of the
gene, which polymorphisms exist, and how these polymorphisms correlate with
disease. This requires the sequence analysis of many DNA samples from a large
number of affected and unaffected individuals.
 
    Affymetrix intends to use its GeneChip technology to become a world leader
in understanding sequence variability. The Company has recently initiated a
large scale polymorphism project that may be the basis of several future
business opportunities. The Company believes that this polymorphism project may
foster the development of new disease management and therapeutic products.
<PAGE>
                             AVAILABLE INFORMATION
 
    Affymetrix, Inc. ("Affymetrix" or the "Company") is subject to the
informational requirements of the Securities Exchange Act of 1934, as amended
(the "Exchange Act"), and in accordance therewith files reports, proxy
statements and other information with the Securities and Exchange Commission
(the "Commission"). Reports, proxy statements and other information filed by the
Company may be inspected and copied at the public reference facilities
maintained by the Commission at 450 Fifth Street, N.W., Washington, D.C. 20549,
and at the Commission's regional offices located at 7 World Trade Center, 7th
Floor, New York, New York 10048 and 500 West Madison Street, Suite 1400,
Chicago, Illinois 60661. Copies of such materials may be obtained from the web
site that the Commission maintains at http://www.sec.gov. In addition, such
materials may also be inspected and copied at the offices of the Nasdaq Stock
Market at 1735 K Street, N.W., Washington, D.C. 20006.
 
    The Company has filed with the Commission a registration statement under the
Securities Act of 1933, as amended (the "Securities Act"), on Form S-3 (together
with all amendments and exhibits thereto) with respect to the Common Stock
offered hereby. This Prospectus does not contain all of the information set
forth in the Registration Statement and the exhibits and schedules thereto,
certain parts of which have been omitted in accordance with the rules and
regulations of the Commission. For such information, reference is made to the
Registration Statement and the exhibits and schedules thereto.
                               ------------------
 
                INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE
 
    The following documents filed with the Commission (File No. 0-28218)
pursuant to the Exchange Act are incorporated by reference:
 
    1.  the Company's Annual Report on Form 10-K for the fiscal year ended
       December 31, 1996;
 
    2.  the Company's Proxy Statement for its annual meeting of shareholders
       held June 6, 1997;
 
    3.  the Company's Quarterly Reports on Form 10-Q for the fiscal quarters
       ended March 31, 1997 and June 30, 1997;
 
    4.  the description of the Company's Common Stock contained in the
       registration statement filed under the Exchange Act registering such
       Common Stock under Section 12 of the Exchange Act; and
 
    5.  all other documents filed by the Company pursuant to Section 13(a),
       13(c), 14 or 15(d) of the Exchange Act subsequent to the date of this
       Prospectus and prior to the termination of the offering of the Common
       Stock.
 
    The Company will provide without charge to each person, including any
beneficial owner, to whom a copy of this Prospectus is delivered, upon the
written or oral request of any such person, a copy of any or all of the
documents which are incorporated herein by reference, other than exhibits to
such information (unless such exhibits are documents which are specifically
incorporated by reference into such documents). Requests for copies should be
directed to: Affymetrix, Inc., 3380 Central Expressway, Santa Clara, CA 95051,
Attention: Investor Relations, Telephone (408) 731-5000.
                               ------------------
 
    Any statement contained in a document all or a portion of which is
incorporated or deemed to be incorporated by reference herein shall be deemed to
be modified or superseded for purposes of this Prospectus to the extent that a
statement contained herein or in any other subsequently filed document which
also is or is deemed to be incorporated by reference herein modifies or
supersedes such statement. Any statement so modified shall not be deemed to
constitute a part of this Prospectus except as so modified, and any statement so
superseded shall not be deemed to constitute a part of this Prospectus.
 
                               ------------------
 
    CERTAIN PERSONS PARTICIPATING IN THE OFFERINGS MAY ENGAGE IN TRANSACTIONS
THAT STABILIZE, MAINTAIN OR OTHERWISE AFFECT THE PRICE OF THE COMMON STOCK,
INCLUDING OVER-ALLOTMENT, STABILIZING AND SHORT-COVERING TRANSACTIONS IN SUCH
SECURITIES, AND THE IMPOSITION OF A PENALTY BID, IN CONNECTION WITH THE
OFFERINGS. IN ADDITION, CERTAIN UNDERWRITERS (AND SELLING GROUP MEMBERS, IF ANY)
ALSO MAY ENGAGE IN PASSIVE MARKET MAKING TRANSACTIONS IN THE COMMON STOCK ON THE
NASDAQ NATIONAL MARKET, IN ACCORDANCE WITH RULE 103 UNDER THE SECURITIES
EXCHANGE ACT OF 1934. FOR A DESCRIPTION OF THESE ACTIVITIES, SEE "UNDERWRITING."
 
                                       3
<PAGE>
                               PROSPECTUS SUMMARY
 
    THE FOLLOWING SUMMARY IS QUALIFIED IN ITS ENTIRETY BY THE MORE DETAILED
INFORMATION AND THE FINANCIAL STATEMENTS AND NOTES THERETO APPEARING ELSEWHERE
IN THIS PROSPECTUS OR INCORPORATED BY REFERENCE HEREIN. UNLESS OTHERWISE
INDICATED, ALL INFORMATION CONTAINED IN THIS PROSPECTUS ASSUMES NO EXERCISE OF
THE UNDERWRITERS' OVER-ALLOTMENT OPTIONS.
 
                                  THE COMPANY
 
    Affymetrix is recognized as a worldwide leader in the field of DNA chip
technology. The Company has developed and intends to establish its
GeneChip-Registered Trademark- system as the platform of choice for acquiring,
analyzing and managing complex genetic information in order to improve the
diagnosis, monitoring and treatment of disease. The Company's GeneChip system
consists of disposable DNA probe arrays containing gene sequences on a chip, a
scanner and other instruments to process the probe arrays and software to
analyze and manage genetic information from the probe arrays.
 
    Affymetrix' strategy is to capitalize on its leadership position in the DNA
probe array field by applying its GeneChip technology primarily to genomics,
disease management and polymorphism discovery. In genomics, Affymetrix intends
to commercialize the expression monitoring applications of its GeneChip system
for use in identifying and validating novel targets for drug discovery. In
disease management, the Company is developing assays, which it believes will
facilitate more efficient patient management in infectious diseases, cancer and
other areas, including drug metabolism. In polymorphism discovery, Affymetrix
has initiated a large scale research project to identify common variations in
the human genome, create databases of these polymorphisms and design GeneChip
probe arrays to analyze these polymorphisms and link them to human disease.
 
    The Company commenced commercial sales of its GeneChip system in April 1996
and currently sells its products to pharmaceutical and biotechnology companies,
academic research centers and clinical reference laboratories. The Company
offers both custom and standard configurations of its GeneChip probe arrays to
customers under a variety of access plans tailored to meet customer needs, such
as the high-volume EasyAccess-TM- program subscribed to by F. Hoffmann-La Roche
Ltd.
 
    In addition, the Company will continue to enter into collaborations to
expand the utilization and applications of its GeneChip technology. The Company
generally structures collaborations to generate research funding and probe array
sales, as well as earn future milestone and royalty payments on sales of drugs
or other products developed using its GeneChip technology.
 
                              RECENT DEVELOPMENTS
 
    GENECHIP TECHNOLOGY PLATFORM ESTABLISHED.  To date, Affymetrix has placed 38
GeneChip systems for research use. A second generation scanner, manufactured by
Hewlett-Packard Company, was introduced in April 1997.
 
    MANUFACTURING INFRASTRUCTURE OPERATIONAL.  The Company's Sunnyvale,
California plant, currently capable of producing 80,000 GeneChip probe arrays
per year, is being expanded.
 
    INTELLECTUAL PROPERTY POSITION STRENGTHENED.  The Company has been issued 27
United States patents and 78 patent applications are pending. The Company has
also licensed rights to important patents related to genetic information and
technologies.
 
    GENOMICS CUSTOMER BASE ESTABLISHED.  Customers include Genetics Institute
Inc., Glaxo Wellcome plc, Hoechst Marion Roussel, Inc., Merck & Co. Inc., the
Parke-Davis division of Warner-Lambert Company, Pfizer Inc. and Pioneer Hi-Bred
International, Inc. In August 1997, F. Hoffmann-La Roche Ltd. became the
Company's first EasyAccess-TM- customer.
 
                                       4
<PAGE>
    DISEASE MANAGEMENT GENECHIP PRODUCTS COMMERCIALIZED.  The Company began
shipments of its products for genetic analysis of HIV in April 1996 and for the
p53 tumor suppressor gene in July 1997. Affymetrix has established
collaborations with bioMerieux Vitek Inc., Glaxo Wellcome plc and OncorMed, Inc.
in bacteriology, virology and oncology, respectively.
 
    POLYMORPHISM DISCOVERY AND DATABASE PROJECT INITIATED.  Internal and
collaborative efforts have identified nearly 2,000 genetic markers. Affymetrix
entered into a consortium with Bristol-Myers Squibb Company and Millennium
Pharmaceuticals, Inc. to fund research at the Whitehead Institute/MIT Center for
Genome Research to identify novel genetic markers and study their role in
disease.
 
    The Company's executive offices are located at 3380 Central Expressway,
Santa Clara, California 95051. The Company's telephone number is (408) 731-5000.
 
                                  RISK FACTORS
 
    The shares of Common Stock offered hereby involve a high degree of risk. See
"Risk Factors" on pages 7 through 21.
 
                               THE OFFERINGS (1)
 
<TABLE>
<S>                                               <C>
Shares of Common Stock offered by the Company:
  U.S. Offering.................................  1,200,000 shares
  International Offering........................  300,000 shares
                                                  ----------------
      Total.....................................  1,500,000 shares
                                                  ----------------
                                                  ----------------
Total shares of Common Stock to be outstanding
 after the Offerings (2)........................  24,200,521 shares
Use of Proceeds.................................  For capital expenditures (manufacturing
                                                  scale-up, expansion of research and
                                                  development facilities, laboratory
                                                  equipment and information systems),
                                                  research and development (including
                                                  product development and core research),
                                                  expansion of sales and marketing, working
                                                  capital and other general corporate
                                                  purposes. See "Use of Proceeds."
Nasdaq National Market symbol...................  "AFFX"
</TABLE>
 
- --------------
 
(1) The offering of 1,200,000 shares of Common Stock initially being offered in
    the United States (the "U.S. Offering") and the concurrent offering of
    300,000 shares of Common Stock initially being offered outside the United
    States (the "International Offering") are collectively referred to as the
    "Offerings". The underwriters for the U.S. Offering (the "U.S.
    Underwriters") and the underwriters for the International Offering (the
    "International Underwriters") are collectively referred to as the
    "Underwriters."
 
(2) Excludes an aggregate of 2,920,783 shares of Common Stock issuable upon
    exercise of outstanding options under the Company's 1993 Stock Plan and 1996
    Nonemployee Directors' Stock Option Plan (the "Stock Plans") and 203,881
    shares issuable upon the exercise of warrants outstanding as of September
    30, 1997. See Note 7 of Notes to Financial Statements.
 
                                       5
<PAGE>
                             SUMMARY FINANCIAL DATA
                     (IN THOUSANDS, EXCEPT PER SHARE DATA)
 
<TABLE>
<CAPTION>
                                                                                                          SIX MONTHS
                                                          YEAR ENDED DECEMBER 31,                       ENDED JUNE 30,
                                         ---------------------------------------------------------  ----------------------
                                            1992       1993        1994        1995        1996        1996        1997
                                         ----------  ---------  ----------  ----------  ----------  ----------  ----------
                                                                                                         (UNAUDITED)
<S>                                      <C>         <C>        <C>         <C>         <C>         <C>         <C>
STATEMENT OF OPERATIONS DATA:
Revenue:
  Product..............................  $       --  $      --  $       --  $       --  $    1,389  $      457  $    1,362
  Contract and grant...................          43      1,413       1,574       4,625      10,583       3,258       6,188
                                         ----------  ---------  ----------  ----------  ----------  ----------  ----------
    Total revenue......................          43      1,413       1,574       4,625      11,972       3,715       7,550
Costs and expenses:
  Cost of product revenue..............          --         --          --          --       2,178         707       1,844
  Research and development.............       4,106      6,566       9,483      12,420      18,762       8,310      12,710
  General and administrative...........         582        577       2,303       3,833       7,569       3,550       5,815
                                         ----------  ---------  ----------  ----------  ----------  ----------  ----------
    Total costs and expenses...........       4,688      7,143      11,786      16,253      28,509      12,567      20,369
                                         ----------  ---------  ----------  ----------  ----------  ----------  ----------
Loss from operations...................      (4,645)    (5,730)    (10,212)    (11,628)    (16,537)     (8,852)    (12,819)
Interest income (expense), net.........         (15)       138         532         881       4,310       1,154       2,687
                                         ----------  ---------  ----------  ----------  ----------  ----------  ----------
Net loss...............................  $   (4,660) $  (5,592) $   (9,680) $  (10,747) $  (12,227) $   (7,698) $  (10,132)
                                         ----------  ---------  ----------  ----------  ----------  ----------  ----------
                                         ----------  ---------  ----------  ----------  ----------  ----------  ----------
Historical net loss per share..........                                                                         $    (0.45)
                                                                                                                ----------
                                                                                                                ----------
Shares used in computing historical net
 loss per share........................                                                                             22,594
Pro forma net loss per share(1)........              $   (0.52) $    (0.55) $    (0.61) $    (0.61) $    (0.43)
                                                     ---------  ----------  ----------  ----------  ----------
                                                     ---------  ----------  ----------  ----------  ----------
Shares used in computing pro forma net
 loss per share(1).....................                 10,715      17,653      17,664      20,131      17,782
</TABLE>
 
<TABLE>
<CAPTION>
                                                                                             JUNE 30, 1997
                                                                                     -----------------------------
BALANCE SHEET DATA:                                                                     ACTUAL     AS ADJUSTED(2)
                                                                                     ------------  ---------------
                                                                                              (UNAUDITED)
<S>                                                                                  <C>           <C>
 
Cash, cash equivalents, and short-term investments.................................  $     94,645   $     153,305
Total assets.......................................................................       111,500         170,160
Long-term obligations..............................................................           619             619
Accumulated deficit................................................................       (54,875)        (54,875)
Total shareholders' equity.........................................................       102,762         161,422
</TABLE>
 
- --------------
 
(1) Computed on the basis described in Note 2 of Notes to Financial Statements.
 
(2) As adjusted to reflect the sale of 1,500,000 shares of Common Stock in the
    Offerings at an assumed public offering price of $41.625 per share and the
    receipt of the estimated net proceeds therefrom. See "Use of Proceeds."
 
                                       6
<PAGE>
                                  RISK FACTORS
 
    IN ADDITION TO THE OTHER INFORMATION IN THIS PROSPECTUS, PROSPECTIVE
PURCHASERS OF THE COMMON STOCK OFFERED HEREBY SHOULD CONSIDER CAREFULLY THE
FOLLOWING RISK FACTORS IN EVALUATING THE COMPANY AND ITS BUSINESS. THIS
PROSPECTUS CONTAINS FORWARD-LOOKING STATEMENTS WITHIN THE MEANING OF THE "SAFE
HARBOR" PROVISIONS OF THE PRIVATE SECURITIES LITIGATION REFORM ACT OF 1995.
REFERENCE IS MADE IN PARTICULAR TO THE DESCRIPTION OF THE COMPANY'S PLANS AND
OBJECTIVES FOR FUTURE OPERATIONS, ASSUMPTIONS UNDERLYING SUCH PLANS AND
OBJECTIVES, AND OTHER FORWARD-LOOKING STATEMENTS INCLUDED IN THE SECTIONS
ENTITLED "PROSPECTUS SUMMARY," "MANAGEMENT'S DISCUSSION AND ANALYSIS OF
FINANCIAL CONDITION AND RESULTS OF OPERATIONS" AND "BUSINESS" HEREIN. SUCH
STATEMENTS ARE BASED ON MANAGEMENT'S CURRENT EXPECTATIONS AND ARE SUBJECT TO A
NUMBER OF FACTORS AND UNCERTAINTIES WHICH COULD CAUSE ACTUAL RESULTS TO DIFFER
MATERIALLY FROM THOSE DESCRIBED IN THE FORWARD-LOOKING STATEMENTS. FACTORS WHICH
COULD CAUSE SUCH RESULTS TO DIFFER MATERIALLY FROM THOSE DESCRIBED IN THE
FORWARD-LOOKING STATEMENTS INCLUDE THOSE SET FORTH IN THE RISK FACTORS BELOW.
 
EARLY STAGE OF DEVELOPMENT
 
    The Company has not commercialized significant quantities of products based
on its technologies. As of September 30, 1997, the Company had placed 38
GeneChip systems, all of which have been solely for research use. The Company's
GeneChip system and other potential products will require significant additional
development and investment, including testing to further validate performance
and demonstrate cost-effectiveness. While the Company's initial product sales
for research use have not required regulatory approval, the Company expects that
such approval will be required for some applications in the future. The Company
or its partners may need to undertake costly and time-consuming efforts to
obtain this approval. There can be no assurance that any future products will be
successfully developed, be proven to be accurate and efficacious in any markets,
meet applicable regulatory standards in a timely manner or at all, be protected
from competition by others, avoid infringing the proprietary rights of others,
be manufactured in sufficient quantities or at reasonable costs, or be marketed
successfully.
 
    The Company has experienced significant operating losses since inception and
expects these losses to continue for at least the next several years. Whether
the Company can successfully manage the transition to a commercial-scale
enterprise will depend upon a number of factors including establishing its
commercial manufacturing capability, developing its marketing capabilities,
establishing sales, marketing and distribution capabilities, as well as entering
into supply agreements with customers desiring to use the Company's products.
Failure to make such a transition successfully would have a material adverse
effect on the Company's business, financial condition and results of operations.
 
TECHNOLOGICAL UNCERTAINTY
 
    The Company is developing its GeneChip system for genomics, disease
management and polymorphism discovery applications. The GeneChip system involves
several new technologies, including a complex chemical synthesis process
necessary to create DNA probe arrays. Technicians using the GeneChip system
require new technical skills and training. There can be no assurance that
technicians will not experience difficulties with the system that would prevent
or limit its use. The instrumentation and software that comprise the GeneChip
system are new and have only recently been used in commercial applications. As
the system continues to be used, it is possible that previously unrecognized
defects will emerge. In addition, DNA probe arrays are tested only on a random
sample basis, and quality problems could develop with the untested arrays.
Further, in order for the Company to address new applications for the GeneChip
system, the Company may be required to increase the number of features on these
arrays and design software capable of managing the information generated from
such probe arrays.
 
                                       7
<PAGE>
There can be no assurance that the Company will be capable of validating or
achieving the improvements in the components of the GeneChip system necessary
for its continued successful commercialization.
 
    The development of research and disease management products based on the
Company's technologies will be subject to the risks of failure inherent in the
development of products based on new technologies. These risks include
possibilities that any products based on these technologies will be found to be
ineffective, unreliable or unsafe, or otherwise fail to receive necessary
regulatory clearances; that products will be difficult to manufacture on a large
scale or will be uneconomical to market; that proprietary rights of third
parties will preclude the Company or its collaborative partners from marketing
products; or that third parties will market superior or equivalent products.
Furthermore, there can be no assurance that the Company's research and
development activities will continue to result in any commercially viable
products.
 
INTENSE COMPETITION; RAPID TECHNOLOGICAL CHANGE
 
    Genomics, disease management and polymorphism discovery technologies have
undergone and are expected to continue to undergo rapid and significant change.
The Company's future success will depend in large part on its ability to
maintain a competitive position with respect to these technologies. Rapid
technological development by the Company or others may result in products or
technologies becoming obsolete. In addition, products offered by the Company
would be made obsolete by less expensive or more effective tests based on other
technologies or by new therapeutic or prophylactic agents that obviate the need
for diagnostic and monitoring information. There can be no assurance that the
Company will be able to make the enhancements to its technology necessary to
compete successfully with newly emerging technologies.
 
    Competition in genomics, disease management and polymorphism discovery is
intense and expected to increase. Further, the technologies for discovering
genes and polymorphisms associated with significant diseases and approaches for
commercializing those discoveries are new and rapidly evolving.
 
    Currently, the Company's principal competition comes from existing
technologies that are used to perform many of the same functions for which the
Company plans to market its GeneChip systems. In the diagnostic field, these
technologies are provided by established diagnostic companies such as Abbott
Laboratories, Roche Boehringer Mannheim, Johnson & Johnson and SmithKline
Beecham plc. These technologies include a variety of established assays, such as
immunoassays, histochemistry, flow cytometry and culture, and newer DNA probe
diagnostics to analyze certain limited amounts of genetic information.
 
    In the genomics and polymorphism discovery fields, existing competitive
technologies include gel-based sequencing using instruments provided by
companies such as the Applied Biosystems division of Perkin-Elmer and Amersham
Pharmacia Biotech Ltd. In order to compete against existing technologies, the
Company will need to demonstrate to potential customers that the GeneChip system
provides improved performance and capabilities. Future competition in these
fields will likely come from existing competitors as well as other companies
seeking to develop new technologies for sequencing and analyzing genetic
information. In addition, pharmaceutical and biotechnology companies, such as
Genome Therapeutics Corporation ("Genome Therapeutics"), Genset S.A. ("Genset"),
Human Genome Sciences, Inc. ("HGS"), Incyte Pharmaceuticals, Inc. ("Incyte"),
Millennium Pharmaceuticals Inc. ("Millennium"), Myriad Genetics, Inc. ("Myriad")
and Sequana Therapeutics, Inc. ("Sequana"), have significant needs for genomic
information and may choose to develop or acquire competing technologies to meet
these needs. Other companies, such as CuraGen, Inc. ("CuraGen"), Digital Gene
Technologies, Inc. ("Digital Gene Technologies"), Gene Logic Inc. ("Gene
Logic"), Hyseq, Inc. ("Hyseq"), Nanogen, Inc. ("Nanogen"), Synteni, Inc.
("Synteni") and Visible Genetics Inc. ("Visible Genetics"),
 
                                       8
<PAGE>
also are developing or have developed DNA probe based assays or other products
and services, some of which may be competitive with those of the Company.
 
    The market for disease management products derived from gene discovery is
currently limited and will be highly competitive. Many companies are developing
and marketing DNA probe tests for genetic and other diseases. Other companies
are conducting research on new technologies for diagnostic tests based on
advances in genetic information. Established diagnostic companies could provide
significant competition to the Company through the development of new products.
These companies have the strategic commitment to diagnostics, the financial and
other resources to invest in new technologies, substantial intellectual property
portfolios, substantial experience in new product development regulatory
expertise, manufacturing capabilities and the distribution channels to deliver
products to customers. These companies also have an installed base of
instruments in several markets, including clinical and reference laboratories,
which are not compatible with the GeneChip system. In addition, these companies
have formed alliances with genomics companies which provide them access to
genetic information that may be incorporated into their diagnostic tests.
 
UNCERTAINTY OF MARKET ACCEPTANCE
 
    The commercial success of the Company's GeneChip system will depend upon
market acceptance by pharmaceutical and biotechnology companies, academic
research centers and clinical reference laboratories. Market acceptance will
depend on many factors, including convincing researchers that the GeneChip
system is an attractive alternative to current technologies for the acquisition,
analysis and management of genetic information; the receipt of regulatory
clearances in the United States, Europe, Japan and elsewhere; the need for
laboratories to license other technologies, such as amplification technologies
that may be required to use the GeneChip system for certain applications; and
the availability of new proprietary markers that may be important to the
diagnosis, monitoring and treatment of disease for incorporation into the
Company's probe arrays. Further, ethical concerns may limit the use of the
GeneChip system for certain disease management applications or the analysis of
genetic information. In addition, potential customers will need skilled
laboratory technicians to operate the GeneChip system. Market acceptance of the
GeneChip system could also be adversely affected by limited funding available
for academic research centers and other research organizations that are the
potential customers for the GeneChip system.
 
    The costs of the GeneChip system and access to probe arrays may deter
certain potential customers of the Company's products. The Company may be
required to discount the price of its GeneChip system or probe arrays.
Furthermore, the failure of the Company to place sufficient quantities of the
instruments for the GeneChip system would have a material adverse effect on its
ability to sell the disposable probe arrays. There can be no assurance that
pharmaceutical or biotechnology companies, academic research centers or clinical
reference laboratories will replace existing instrumentation and techniques with
the GeneChip system. Because of these and other factors, there can be no
assurance that the Company's products will gain market acceptance.
 
    The Company expects that its customers will be concentrated in a small
number of pharmaceutical and biotechnology companies, academic research centers
and clinical reference laboratories. As a result, the Company's financial
performance may depend on large orders from a limited number of customers. There
are only three major reference laboratories in the United States, two of which
are associated with large pharmaceutical companies. There can be no assurance
that the Company will be able to market successfully the GeneChip system to
reference laboratories or that the affiliation of these laboratories with
pharmaceutical companies will not adversely affect their decision to purchase
GeneChip systems. The Company's dependence on sales to a few large reference
laboratories may also strengthen the purchasing leverage of these potential
customers, which could reduce the sales price of the GeneChip system. Also, the
Company believes that the sales cycle for the GeneChip system will be lengthy
due to the need to educate potential customers about its characteristics. The
failure of the
 
                                       9
<PAGE>
Company to gain additional customers, the loss of any customer or a significant
reduction in the level of sales to any customer would have a material adverse
effect on the Company's business, financial condition and results of operations.
 
UNCERTAINTIES RELATED TO COMMERCIAL VIABILITY OF EXISTING PRODUCTS
 
    The first commercial application of the Company's GeneChip system is a HIV
probe assay designed to detect mutations in HIV, the virus that causes AIDS. The
HIV probe array provides sequence information from the reverse transcriptase and
protease genes of HIV, and the system includes a fluidics station, a scanner and
related software. In April 1996, the Company introduced the HIV probe array for
research purposes only. In July 1997, the Company introduced its second
commercially available product, the p53 tumor suppressor gene assay for research
use, which was developed in collaboration with OncorMed Inc., ("OncorMed"). The
Company has also entered into several supply and collaborative agreements
pursuant to which it is supplying GeneChip systems and expression probe arrays
for research purposes. As of September 30, 1997, the Company had placed 38
GeneChip systems at customer sites. These systems have been in operation for a
limited period of time, and their accuracy and efficacy have not been fully
demonstrated. There can be no assurance that the accuracy of the probe arrays in
providing sequence information will be equal to or better than current
technologies, such as gel-based sequencing techniques.
 
    There can be no assurance that the probe arrays will provide commercially
useful information, that the arrays or the GeneChip system will operate without
difficulties, that technicians will have adequate training to use the GeneChip
system, or that the Company will not experience manufacturing problems or
marketing difficulties selling the probe arrays to pharmaceutical and
biotechnology companies, academic research centers and clinical reference
laboratories. Furthermore, there can be no assurance that the HIV or p53 assays
will gain regulatory approval for clinical use. As new therapies and
combinations of therapies for treating HIV are employed, new mutations in the
HIV genome may be discovered that would require the Company to redesign its
current HIV probe array or develop new probe arrays. Advanced therapies could be
discovered that target other components of the virus or which do not generate
drug resistance. Similarly, new mutations identified in the p53 gene may require
the Company to redesign its current p53 probe assay or develop new probe assays.
Cost containment pressures for treating diseases, including HIV and cancer, may
limit the price the Company may be able to charge potential customers for these
probe arrays. Failure of the Company to successfully commercialize its HIV, p53
and gene expression probe arrays could have a material adverse effect on the
Company's business, financial condition and results of operations and may
adversely affect the Company's ability to commercialize future products.
 
DEPENDENCE UPON COLLABORATIVE PARTNERS
 
    An important element of the Company's business strategy involves
collaborations with pharmaceutical, diagnostic and biotechnology companies that
have discovered genes and may seek to use the Company's technologies to discover
genetic mutations or develop diagnostic and therapeutic products. The Company
has significant collaborations with Hewlett-Packard Company ("HP"), bioMerieux
Vitek, Inc. ("bioMerieux"), Incyte and OncorMed, and has entered into a
consortium with the Whitehead Institute MIT/Center for Genome Research (the
"Whitehead Institute"), Millennium and Bristol-Myers Squibb Company
("Bristol-Myers").
 
    The Company has received a material portion of its revenue since inception
from its collaborative partners and intends to enter into collaborative
arrangements with other companies to apply its technology, fund development,
commercialize potential future products, and assist in obtaining regulatory
approval. There can be no assurance that any of the Company's present or future
collaborative partners will perform their obligations as expected or will devote
sufficient resources to the development, clinical testing or marketing of the
Company's potential products developed under the collaborations. Any
 
                                       10
<PAGE>
parallel development by a partner of technologies or components competitive with
the GeneChip system, preclusion of the Company from entering into competitive
arrangements, failure to obtain timely regulatory approvals, premature
termination of an agreement, or failure by a partner to devote sufficient
resources to the development and commercialization of the Company's products
could have a material adverse effect on the Company's business, financial
condition and results of operations.
 
    The Company's agreements with its collaborators may have provisions that
give rise to disputes regarding the rights and obligations of the parties. These
and other possible disagreements could lead to delays in collaborative research,
development or commercialization of certain products, or could require or result
in litigation or arbitration, which would be time-consuming and expensive, and
could have a material adverse effect on the Company's business, financial
condition and results of operations.
 
    There can be no assurance that the Company will be able to negotiate future
collaborative arrangements on acceptable terms, if at all, or that such
collaborations will be successful.
 
HISTORY OF LOSSES AND EXPECTATION OF FUTURE LOSSES
 
    The Company has incurred operating losses in each year since its inception,
including net losses of approximately $10.7 million during the year ended
December 31, 1995 and $12.2 million during the year ended December 31, 1996 and
$10.1 million during the six months ended June 30, 1997. At June 30, 1997, the
Company had an accumulated deficit of approximately $54.9 million. The Company's
losses have resulted principally from costs incurred in research and development
and from general and administrative costs associated with the Company's
operations. These costs have exceeded the Company's interest income and revenues
which, to date, have been generated principally from collaborative research and
development agreements, supply agreements and government research grants. The
Company expects to incur substantial additional operating losses over the next
several years as a result of increases in its expenses for research and product
development, manufacturing scale-up, expanding sales and marketing and capital
expenditures.
 
    The Company may have to discount the price of the GeneChip system to gain
market acceptance, which could adversely affect gross margins. The Company's
future gross margins, if any, will be dependent on, among other factors, the
Company's ability to cost-effectively manufacture the GeneChip system, its
product mix and the degree of price discounts required to market its products to
pharmaceutical and biotechnology companies, academic research centers and
clinical reference laboratories.
 
    The amount of future operating losses and time required by the Company to
reach profitability, if ever, are highly uncertain. The Company's ability to
generate significant revenues and become profitable is dependent in large part
on the ability of the Company to enter into additional customer supply
agreements and collaborative arrangements and on the ability of the Company and
its collaborative partners to successfully commercialize products developed
under the collaborations.  In addition, delays in receipt of any necessary
regulatory approvals by the Company or its collaborators, or receipt of
approvals by competitors, could adversely affect the successful
commercialization of the Company's technologies. There can be no assurance that
the Company will ever achieve profitability.
 
FLUCTUATIONS IN OPERATING RESULTS
 
    The Company's quarterly operating results depend upon the volume and timing
of orders for GeneChip systems and probe arrays received and delivered during
the quarter, variations in revenue recognized under supply and collaborative
agreements, including license fees, product sales, milestones, royalties and
other contract revenues, as well as the timing of new product introductions by
the Company. The Company's quarterly operating results may also fluctuate
significantly depending on other factors, including the introduction of new
products by the Company's competitors; regulatory actions; market acceptance of
the GeneChip system and other potential products; adoption of new
 
                                       11
<PAGE>
technologies; manufacturing capabilities; variations in gross margins of the
Company's products; competition; the cost, quality and availability of reagents
and components; the mix of products sold; changes in government funding; and
third-party reimbursement policies.
 
DEPENDENCE ON PROPRIETARY TECHNOLOGY AND UNPREDICTABILITY OF PATENT PROTECTION
 
    Affymetrix has been issued 27 patents in the United States and holds over 78
pending United States patent applications. Many of these patents and
applications have been filed and/or issued in one or more foreign countries.
Affymetrix also relies upon copyright protection, trade secrets, know-how,
continuing technological innovation and licensing opportunities to develop and
maintain its competitive position. The Company's success will depend in part on
its ability to obtain patent protection for its products and processes, to
preserve its copyrights and trade secrets to operate without infringing the
proprietary rights of third parties and to acquire licenses related to enabling
technologies or products.
 
    The Company is party to various license option and license agreements with
third parties (including Stanford University, Scientific Generics, Ltd.,
Concordia University, OncorMed and the University of California) which give it
rights to use certain technologies. Failure of the Company to maintain rights to
such technology could have a material adverse effect on the Company's business,
financial condition and results of operations. For example, inability of the
Company to exercise the option for the Stanford University technology relating
to HIV under commercially reasonable terms could have an adverse effect on the
ability of the Company to sell its HIV probe assays.
 
    The patent positions of pharmaceutical and biotechnology companies,
including the Company, are generally uncertain and involve complex legal and
factual questions. There can be no assurance that any of the Company's pending
patent applications will result in issued patents, that the Company will develop
additional proprietary technologies that are patentable, that any patents issued
to the Company or its strategic partners will provide a basis for commercially
viable products or will provide the Company with any competitive advantages or
will not be challenged by third parties, or that the patents of others will not
have an adverse effect on the ability of the Company to do business. In
addition, patent law relating to the scope of claims in the technology fields in
which the Company operates is still evolving. The degree of future protection
for the Company's proprietary rights, therefore, is uncertain. Furthermore,
there can be no assurance that others will not independently develop similar or
alternative technologies, duplicate any of the Company's technologies, or, if
patents are issued to the Company, design around the patented technologies
developed by the Company. In addition, the Company could incur substantial costs
in litigation to defend itself in patent suits brought by third parties, or if
it initiates such suits.
 
    The commercial success of the Company also depends in part on the Company
neither infringing patents or proprietary rights of third parties nor breaching
any licenses that may relate to the Company's technologies and products. For
example, the Company, its collaborators and customers may need to acquire a
license for an amplification technology to use the GeneChip system in certain
applications, and there is no assurance such a license will be available on
commercially reasonable terms. Furthermore, the Company is aware of third-party
patents that may relate to the Company's technology, including reagents used in
probe array synthesis and in probe array assays, probe array scanners, synthesis
techniques, oligonucleotide amplification techniques, assays, and probe arrays.
There can be no assurance that the Company will not infringe on these patents or
other patents or proprietary rights of third parties or that the Company would
be able to obtain a license to such patents or proprietary rights on
commercially acceptable terms, if at all. In addition, the Company has received
and may in the future receive a notice claiming infringement from third parties
as well as invitations to take licenses under third party patents.
 
    The Company is aware of patents and patent applications owned by Isis
Innovation Ltd. (E.M. Southern) that may relate to the Company's technology. The
Company has opposed two such allowed
 
                                       12
<PAGE>
European patents. One such patent has also been issued in the United States, and
the Company is aware that others are pending and may issue. One of the allowed
European applications has broad claims to certain array related technology,
which claims have been opposed by the Company. If a United States patent
relating to arrays issues with claims as broad as the European patent, the
Company could be subject to infringement claims that could delay or preclude
sales of some or all of its products, which would have a material adverse effect
on the Company's business, financial condition and results of operations. If the
Company were required to obtain a license to any such patent, there can be no
assurance that such license could be acquired on commercially acceptable terms,
if at all.
 
    On March 3, 1997, Hyseq filed a lawsuit in United States District Court for
the Northern District of California (San Jose Division) alleging that certain
Affymetrix products infringe United States patents 5,202,231 and 5,525,464. The
Hyseq action and any other legal action against the Company or its collaborative
partners claiming damages and seeking to enjoin commercial activities relating
to the affected products and processes could, in addition to subjecting the
Company to potential liability for damages, require the Company or its
collaborative partners to obtain a license in order to continue to manufacture
or market the affected products and processes. While the Company believes the
Hyseq complaint is without merit, there can be no assurance that the Company
will prevail in the Hyseq action or that the Company or its collaborative
partners will prevail in any other action, nor can there be any assurance that
any license (including licenses proposed by third parties) required would be
made available on commercially acceptable terms, if at all.
 
    There are a significant number of United States and foreign patents and
patent applications in the Company's areas of interest, and the Company believes
that there may be significant litigation in the industry regarding patent and
other intellectual property rights. The Hyseq action and any other such
litigation could consume substantial managerial and financial resources, which
could have a material adverse effect on the Company's business, financial
condition and results of operations. Further, because of the substantial amount
of discovery required in connection with any such litigation, there is a risk
that confidential information could be compromised by disclosure.
 
    Others may have filed and in the future are likely to file patent
applications that are similar or identical to those of the Company or those of
its licensors. To determine the priority of inventions, the Company may have to
participate in interference proceedings declared by the United States Patent and
Trademark Office that could result in substantial cost to the Company. No
assurance can be given that any such patent application will not have priority
over patent applications filed by the Company.
 
    The enactment of legislation implementing the General Agreement on Trade and
Tariffs has resulted in certain changes in United States patent laws that became
effective on June 8, 1995. Most notably, the term of patent protection for
patent applications filed on or after June 8, 1995 is no longer a period of
seventeen years from the date of grant. The new term of United States patents
will commence on the date of issuance and terminate twenty years after the
earliest effective filing date of the application. Because the time from filing
to issuance of biotechnology patent applications in the Company's area of
interest is often more than three years, a twenty-year term after the effective
date of filing may result in a substantially shortened term of the Company's
patent protection which may adversely affect the Company's patent position.
 
    The Company also relies upon copyright and trade secret protection for its
confidential and proprietary information. There can be no assurance, however,
that such measures will provide adequate protection for the Company's trade
secrets or other proprietary information. In addition, there can be no assurance
that proprietary information will not be disclosed, that others will not
independently develop substantially equivalent proprietary information and
techniques or otherwise gain access to the Company's copyrights and trade
secrets or disclose such technology, or that the Company can effectively protect
its trade secrets.
 
                                       13
<PAGE>
    The Company's academic collaborators have certain rights to publish data and
information in which the Company has rights. There is considerable pressure on
academic institutions to publish discoveries in the genetics and genomics
fields. There can be no assurance that such publication would not adversely
affect the Company's ability to obtain patent protection for some genes in which
it may have a commercial interest.
 
NEED FOR ADDITIONAL FUNDING; UNCERTAINTY OF ACCESS TO CAPITAL
 
    The Company anticipates that its existing capital resources, together with
the net proceeds of the Offerings and interest earned thereon, will enable it to
maintain currently planned operations through at least 2000. However, this
expectation is based on the Company's current operating plan, which could change
as a result of many factors, and the Company could require additional funding
sooner than anticipated. In addition, the Company may choose to raise additional
capital due to market conditions or strategic considerations even if it has
sufficient funds for its operating plan. The Company's requirements for capital
will be substantial and will depend on many factors, including payments received
under existing and possible future supply and collaborative agreements; the
availability of government research grant payments; the progress of the
Company's collaborative and independent research and development projects; the
cost of preclinical and clinical trials for the Company's products; the
prosecution, defense and enforcement of patent claims and other intellectual
property rights; and development of manufacturing, marketing and sales
capabilities. The Company has no credit facility or other committed sources of
capital. To the extent capital resources are insufficient to meet future capital
requirements, the Company will have to raise additional funds to continue the
development of its technologies. There can be no assurance that such funds will
be available on favorable terms, or at all. To the extent that additional
capital is raised through the sale of equity or convertible debt securities, the
issuance of such securities could result in dilution to the Company's
shareholders. If adequate funds are not available, the Company may be required
to curtail operations significantly or to obtain funds by entering into
collaboration agreements on unattractive terms. The Company's inability to raise
capital would have a material effect on the Company's business, financial
condition and results of operations. See "Use of Proceeds."
 
LIMITED MANUFACTURING CAPABILITY; SOLE SOURCE SUPPLIERS
 
    The Company has limited experience manufacturing products for commercial
purposes. To date, the Company has a manufacturing facility capable of providing
only limited quantities of probe arrays for internal and collaborative purposes
and initial sales of the GeneChip system to the research market. To achieve the
production levels of probe arrays necessary for successful commercialization of
its products, the Company will need to scale-up its manufacturing facilities and
establish more automated manufacturing capabilities and maintain adequate levels
of inventory to meet customer needs. The Company may also need to comply with
the current good manufacturing practices ("GMPs") prescribed by the United
States Food and Drug Administration ("FDA") for sale of products in the United
States, ISO standards for sale of products in Europe, as well as other standards
prescribed by various federal, state and local regulatory agencies in the United
States and other countries. Although the Company does not currently need to
comply with GMP to manufacture probe arrays and related instrumentation for sale
for research purposes, it may need to be GMP compliant to sell these products to
clinical reference laboratories, and it will need to be compliant to sell these
products for clinical use. There can be no assurance that manufacturing,
inventory and quality control problems will not arise as the Company attempts to
scale-up its manufacturing facilities or that such scale-up can be achieved in a
timely manner or at commercially reasonable costs.
 
    The Company's probe array manufacturing process is complex and involves a
number of technologies that have never before been combined in the manufacture
of a single product. The Company tests only selected probe arrays from each
wafer and only selected probes on such probe arrays. It is therefore possible
that defective probe arrays might not be identified before they are shipped.
After the
 
                                       14
<PAGE>
probe arrays are shipped, only selected probes may be tested by the customer.
The Company therefore relies on quality control procedures, including controls
on the manufacturing process and sample testing, to verify the correct
completion of the manufacturing process. In addition, there may be certain
aspects of the Company's manufacturing that are not fully understood and cannot
be readily replicated for commercial use. If the Company is unable to
manufacture probe arrays on a timely basis because of these or other factors,
its business, financial condition and results of operations could be adversely
affected.
 
    As the Company's technologies evolve, new manufacturing techniques and
systems will be required. For example, it is anticipated that automated
processing systems will be needed to meet the Company's future probe array
manufacturing needs. Further, as products requiring increased density are
developed, miniaturization of the features on the arrays will be necessary,
requiring new or modified manufacturing equipment and processes. Further, the
Company's manufacturing equipment requires significant capital investment.
Although the Company is planning to build a second manufacturing facility, the
Company presently relies on a single manufacturing facility for its probe
arrays. This manufacturing facility is subject to natural disasters such as
earthquakes and floods. The former are of particular significance since the
manufacturing facility is located in an earthquake prone area. In the event that
its manufacturing facility were to be affected by accidental or natural
disasters, the Company would be unable to manufacture products for sale until
the facility was replaced or restored to operation.
 
    In November 1995, the Company entered into an agreement with RELA, Inc.
("RELA"), a private company, for the supply of fluidics stations. RELA
manufactured fluidics stations for the Company pursuant to the agreement until
September 1997. In September 1997, the Company terminated the agreement and
commenced the manufacture of fluidics stations internally. There can be no
assurance that manufacturing and quality control problems will not arise in the
manufacture of the fluidics stations by the Company.
 
    Certain key parts of the GeneChip system, such as the scanner and certain
reagents, are currently available only from a single source or a few sources.
The Company currently obtains the scanners for its GeneChip probe arrays from
HP. The Company is dependent on HP for quality testing and service of this
instrument. No assurance can be given that scanners, reagents or other
components of the GeneChip system will be available in commercial quantities at
acceptable costs. If the Company is required to seek alternative sources of
supply, it could be time consuming and expensive. In addition, the Company is
dependent on its vendors to provide components of appropriate quality and
reliability and to meet applicable regulatory requirements. Consequently, in the
event that supplies from these vendors were delayed or interrupted for any
reason, the Company's ability to develop and supply its products could be
impaired, which could have a material adverse effect on the Company's business,
financial condition and results of operations.
 
LIMITED SALES AND MARKETING EXPERIENCE
 
    The Company does not have a direct sales force and has only limited
experience in sales and marketing. As of September 30, 1997, the Company had
placed 38 GeneChip systems, of which only 28 had been sold. The Company has
placed only three of its GeneChip systems outside the United States. The Company
intends to market its products to pharmaceutical and biotechnology companies,
academic research centers and clinical reference laboratories. The Company may
be required to enter into collaboration or distribution arrangements to
commercialize its products both inside and outside the United States. There can
be no assurance that the Company will be able to establish a direct sales force
or to establish collaborative or distribution arrangements to market its
products. Failure to do so would have a material adverse effect on the Company's
business, financial condition and results of operations.
 
                                       15
<PAGE>
UNCERTAINTIES RELATED TO CONTINUED GOVERNMENT FUNDING
 
    A significant portion of the Company's products for research use are likely
to be sold to universities, government research laboratories, private
foundations and other institutions where funding is dependent upon grants from
government agencies such as the National Institutes of Health ("NIH"). Research
funding by the government, however, may be significantly reduced in the
future.  Any such reduction may materially affect the ability of the Company's
prospective research customers to purchase the Company's products for research
use. The Company has received and expects to continue to receive significant
funds under various United States government research and technology programs.
While the programs are generally multi-year awards, they are subject to a yearly
appropriations process in the United States Congress. There can be no assurance
that the Company will receive the $15.5 million remaining funding designated for
it under the Advanced Technology Program ("ATP") grant, and termination of the
ATP grant could have a material adverse effect on the Company's business,
financial condition and results of operations. The Company's ATP and NIH grants
give the government certain rights to license for its own use inventions
resulting from funded work. There can be no assurance that the Company's
proprietary position will not be adversely affected should the government
exercise these rights.
 
UNCERTAINTIES RELATED TO THIRD-PARTY REIMBURSEMENT
 
    The ability of the Company, its collaborators and other pharmaceutical and
biotechnology companies to successfully commercialize their products may depend
on their ability to obtain adequate levels of reimbursement for certain health
care products and services in the United States, Europe and other countries. The
availability of third-party reimbursement for such products and services may be
limited or uncertain, particularly with respect to genetic tests and other
disease management products.
 
    In the United States, the cost of medical care is funded, in substantial
part, by government insurance programs, such as Medicare and Medicaid, and
private and corporate health insurance plans. Third-party payors may deny
reimbursement if they determine that a prescribed health care product or service
has not received appropriate FDA or other governmental regulatory clearances, is
not used in accordance with cost-effective treatment methods as determined by
the payor, or is experimental, unnecessary or inappropriate. The ability of the
Company, its collaborators and other pharmaceutical and biotechnology companies
to commercialize certain of their products and services successfully may depend
on the extent to which appropriate reimbursement levels for the costs of such
products and services are obtained from government authorities, private health
insurers and other organizations, such as health maintenance organizations
("HMOs"). Third-party payors are increasingly challenging the prices charged for
health care products and services. The trend towards managed health care in the
United States and the concurrent growth of organizations such as HMOs, which
could control or significantly influence the purchase of health care products
and services, as well as legislative proposals to reform health care or reduce
government insurance programs, may all result in lower prices for health care
products and services commercialized by customers and collaborative partners of
the Company. This could reduce the amount of future royalty payments that may be
due to the Company on such product sales or services. The cost containment
measures that health care providers are instituting and the impact of any health
care reform may also adversely affect the profits of the Company's customers and
collaborative partners. As a result, pharmaceutical and biotechnology companies
may choose to reduce or eliminate certain research and development programs that
utilize the Company's products. A reduction of royalty payments to the Company
or the reduction or cancellation of research programs that utilize the Company's
products could have a material adverse effect on the Company's business,
financial condition and results of operations.
 
                                       16
<PAGE>
GOVERNMENT REGULATION; NO ASSURANCE OF REGULATORY APPROVAL
 
    The manufacturing, labeling, distribution and marketing of some or all of
the Company's disease management products are subject to government regulation
in the United States and in certain other countries.
 
    In the United States, the FDA regulates, as medical devices, most diagnostic
tests and in vitro reagents that are marketed as finished test kits or
equipment. Some clinical laboratories, however, purchase individual reagents
intended for specific analyses, and use those reagents to develop and prepare
their own finished diagnostic tests. Although the FDA has not generally
exercised regulatory authority over these individual reagents or the finished
tests prepared from them by the clinical laboratories, the FDA has proposed a
rule that, if adopted, would regulate reagents sold to clinical laboratories as
medical devices. The proposed rule would also restrict sales of these reagents
to clinical laboratories certified under Clinical Laboratory Improvement
Amendments of 1988 ("CLIA") as high complexity laboratories. The Company intends
to market some diagnostic products as finished test kits or equipment and others
as individual reagents; consequently, some or all of these products may be
regulated as medical devices.
 
    The Food, Drug, and Cosmetic Act requires that medical devices introduced to
the United States market, unless exempted by regulation, be the subject of
either a premarket notification clearance (known as a "510(k)") or an approved
premarket approval ("PMA"). Some of the Company's products and those of its
collaborators may require a PMA and others may require a 510(k). With respect to
devices reviewed through the 510(k) process, a company may not market a device
until an order is issued by the FDA finding the product to be substantially
equivalent to a legally marketed device known as a "predicate device." A 510(k)
submission may involve the presentation of a substantial volume of data,
including clinical data, and may require a substantial review. The FDA may agree
that the product is substantially equivalent to a predicate device and allow the
product to be marketed in the United States. The FDA, however, may (i) determine
that the device is not substantially equivalent and require a PMA, or (ii)
require further information, such as additional test data, including data from
clinical studies, before it is able to make a determination regarding
substantial equivalence. By requesting additional information, the FDA can
further delay market introduction of a company's products. If the FDA indicates
that a PMA is required for any of the Company's products, the application will
require extensive clinical studies, manufacturing information (including
demonstration of compliance with GMP requirements) and likely review by a panel
of experts outside the FDA. Clinical studies to support either a 510(k)
submission or a PMA application would need to be conducted in accordance with
FDA requirements. Failure to comply with FDA requirements could result in the
FDA's refusal to accept the data or the imposition of regulatory sanctions. FDA
review of a PMA application could take significantly longer than that for a
510(k).
 
    There can be no assurance that the Company or its collaborators will be able
to meet the FDA's requirements or that any necessary approval will be received.
Once granted, a 510(k) clearance or PMA approval may place substantial
restrictions on how the device is marketed or to whom it may be sold. Even where
a device is exempted from 510(k) clearance or PMA approval, the FDA may impose
restrictions on its marketing. In addition to requiring clearance or approval
for new products, the FDA may require clearance or approval prior to marketing
products that are modifications of existing products. There can be no assurance
that any necessary 510(k) clearance or PMA approval will be granted on a timely
basis or at all. FDA imposed restrictions could limit the number of customers to
whom particular products could be marketed or what may be communicated about
particular products. Delays in receipt of or failure to receive any necessary
510(k) clearance or PMA, or the imposition of stringent restrictions on the
Company's labeling and sales of its products could have a material adverse
effect on the Company.
 
    As a medical device manufacturer, the Company would also be required to
register and list its products with the FDA. In addition, the Company would be
required to comply with the FDA's GMP
 
                                       17
<PAGE>
regulations, which require that medical devices be manufactured and records be
maintained in a prescribed manner with respect to manufacturing, testing and
control activities. Further, the Company would be required to comply with FDA
requirements for labeling and promotion of its medical devices. For example, the
FDA prohibits cleared or approved devices from being marketed for uncleared or
unapproved uses. In addition, the medical device reporting regulation would
require that the Company provide information to the FDA whenever there is
evidence to reasonably suggest that one of its devices may have caused or
contributed to a death or serious injury, or that there has occurred a
malfunction that would be likely to cause or contribute to a death or serious
injury if the malfunction were to recur.
 
    Medical device manufacturers are subject to periodic inspections by the FDA
and state agencies. Additionally, the FDA will conduct a preapproval inspection
for all PMA devices and in some cases for 510(k) devices as well. If the FDA
believes that a company is not in compliance with applicable laws or
regulations, it can institute proceedings to issue a warning or other letter
apprising of violative conduct, detain or seize products, issue a recall, enjoin
future violations and assess civil and criminal penalties against the company,
its officers or its employees. In addition, clearances or approvals could be
suspended or withdrawn in appropriate circumstances. Failure to comply with
regulatory requirements or any adverse regulatory action could have a material
adverse effect on the Company.
 
    Medical device laws and regulations are also in effect in many of the
countries in which the Company may do business outside the United States. These
range from comprehensive device approval requirements for some or all of the
Company's medical device products to requests for product data or
certifications. The number and scope of these requirements are increasing. There
can be no assurance that the Company will obtain regulatory approvals in such
countries or that it will not be required to incur significant costs in
obtaining or maintaining its foreign regulatory approvals. In addition, the
export by the Company of certain of its products which have not yet been cleared
for domestic commercial distribution may be subject to FDA export restrictions.
The failure to obtain product approvals in a timely fashion or to comply with
state or foreign medical device laws and regulations may have a material adverse
impact on the Company. Medical device laws and regulations are also in effect in
some states in which the Company does business.
 
    In addition, federal, state and foreign laws and regulations regarding the
manufacture and sale of medical devices are subject to future changes. For
example, the FDA has recently made significant changes in its regulations
regarding medical device GMPs and is considering changes to other regulations.
The Company cannot predict what impact, if any, such changes might have on its
business; however, such changes could have a material impact on the Company.
 
    Any of the Company's customers using its diagnostic devices for clinical use
in the United States may be regulated under CLIA. CLIA is intended to ensure the
quality and reliability of clinical laboratories in the United States by
mandating specific standards in the areas of personnel qualifications,
administration, participation in proficiency testing, patient test management,
quality control, quality assurance and inspections. The regulations promulgated
under CLIA establish three levels of diagnostic tests ("waived," "moderately
complex" and "highly complex") and the standards applicable to a clinical
laboratory depend on the level of the tests it performs. CLIA requirements may
prevent some clinical laboratories from using certain of the Company's
diagnostic products. In addition, the FDA has proposed regulation of certain
"analyze specific reagents" used in clinical reference laboratories. There can
be no assurance that the CLIA regulations and future administrative
interpretations of CLIA or future regulatory requirements of the FDA will not
have a material adverse impact on the Company by imposing new regulatory
requirements or by limiting the potential market for the Company's products.
 
    The Company is also subject to numerous environmental and safety laws and
regulations, including those governing the storage, use and disposal of
hazardous and biological materials. Any violation of, and the cost of compliance
with, these regulations could have a material adverse effect on the Company's
business, financial condition and results of operations.
 
                                       18
<PAGE>
ETHICAL, LEGAL AND SOCIAL IMPLICATIONS OF GENETIC PREDISPOSITION TESTING
 
    The Company's success will depend in part upon the Company's ability to
develop genetic tests for genes discovered by the Company and others. Genetic
tests, such as certain of the Company's GeneChip assays, may be difficult to
perform and interpret and may lead to misinformation or misdiagnosis. Further,
even when a genetic test identifies the existence of a mutation in an
individual, the interpretation of the result is often limited to the
identification of a statistical probability that the tested individual will
develop the disease or condition for which the test is performed. In addition,
once available, such tests may be subject to ethical concerns or reluctance to
administer or pay for tests for conditions that are not treatable. Further, it
is possible that specific gene-based diagnostic tests marketed by other
companies could encounter public resistance, resulting in societal and
governmental concerns regarding genetic testing in general.
 
    The prospect of broadly available genetic predisposition testing has raised
issues regarding the appropriate utilization and the confidentiality of
information provided by such testing. It is possible that discrimination by
insurance companies could occur through the raising of premiums by insurers to
prohibitive levels, outright cancellation of insurance or unwillingness to
provide coverage to patients shown to have a genetic predisposition to a
particular disease. In addition, employers could discriminate against employees
with a genetic predisposition to develop a particular disease. Finally,
governmental authorities could, for social or other purposes, limit the use of
genetic testing or prohibit testing for genetic predisposition to certain
conditions which could adversely affect the use of the Company's products. There
can be no assurance that ethical concerns about genetic testing will not
adversely affect market acceptance of the Company's GeneChip system.
 
ATTRACTION AND RETENTION OF KEY EMPLOYEES AND SCIENTIFIC ADVISORS
 
    The Company is highly dependent on the principal members of its management
and scientific staff. The loss of services of any of these persons could have a
material adverse effect on the Company's product development and
commercialization efforts. In addition, recruiting and retaining qualified
scientific personnel to perform future research and development work will be
critical to the Company's success. There can be no assurance that the Company
will be able to attract and retain such personnel.
 
    Product development and commercialization will require additional personnel
in areas such as diagnostic testing, regulatory affairs, manufacturing and
marketing. The inability to acquire such services or to develop such expertise
could have a material adverse effect on the Company's business, financial
condition and results of operations.
 
    In addition, the Company relies on its scientific advisors to assist the
Company in formulating its research and development strategy. All of the
scientific advisors are employed by employers other than the Company and have
commitments to other entities that may limit their availability to the Company.
Some of the Company's scientific advisors also consult for companies that may be
competitors of the Company.
 
EXPOSURE TO PRODUCT LIABILITY CLAIMS
 
    The Company's business exposes it to potential product liability claims that
are inherent in the testing, manufacturing, marketing and sale of human
diagnostic and therapeutic products. The Company intends to acquire additional
insurance, should it be desirable, for clinical liability risks. There can be no
assurance that it will be able to obtain such insurance or general product
liability insurance on acceptable terms or at reasonable costs or that such
insurance will be in sufficient amounts to provide the Company with adequate
coverage against potential liabilities. A product liability claim or recall
could have a material adverse effect on the Company's business, financial
condition and results of operations.
 
                                       19
<PAGE>
BROAD DISCRETION IN ALLOCATION AND USE OF PROCEEDS
 
    The Company expects to use approximately $30.0 million of the net proceeds
of the Offerings for capital expenditures to scale up manufacturing capacity,
expand facilities for research and development, and for laboratory equipment and
information systems. The Company has not yet identified the specific amounts and
uses of approximately $28.7 million (approximately 49%) of the net proceeds. The
Company's Board of Directors and management will retain broad discretion as to
the allocation of the net proceeds of the Offerings. See "Use of Proceeds."
 
CONTROL BY GLAXO, MANAGEMENT AND RELATED PERSONS
 
    Glaxo beneficially owns approximately 33% of the Company's outstanding
Common Stock and executive officers, directors and principal shareholders (other
than Glaxo) beneficially own approximately 7% of the Company's outstanding
Common Stock. Accordingly, Glaxo and these shareholders may be able to influence
the outcome of shareholder votes, including votes concerning the election of
directors, adoption of amendments to the Company's Articles of Incorporation and
Bylaws and approval of mergers and other significant corporate transactions.
Glaxo and the Company have executed a governance agreement that confers rights
on Glaxo in certain circumstances.
 
ANTI-TAKEOVER EFFECT OF CERTAIN CHARTER PROVISIONS
 
    Certain provisions of the Company's Articles of Incorporation and Bylaws and
certain other contractual provisions could have the effect of making it more
difficult for a third party to acquire, or of discouraging a third party from
attempting to acquire, or control the Company. Such provisions could limit the
price that certain investors might be willing to pay in the future for shares of
the Company's Common Stock. Certain of these provisions allow the Company to
issue Preferred Stock with rights senior to those of the Common Stock without
any further vote or action by the shareholders, eliminate the right of
shareholders to act by written consent which could make it more difficult for
shareholders to affect certain corporate actions. These provisions could also
have the effect of delaying or preventing a change in control of the Company.
The issuance of Preferred Stock could decrease the amount of earnings and assets
available for distribution to the holders of Common Stock or could adversely
affect the rights and powers, including voting rights, of the holders of the
Common Stock. In certain circumstances, such issuance could have the effect of
decreasing the market price of the Common Stock.
 
VOLATILITY OF STOCK PRICE
 
    The market price of the Company's Common Stock since the Company's initial
public offering in June 1996 has increased dramatically and has been highly
volatile. In addition to overall stock market fluctuations, factors such as
announcements of results of research activities, collaborative agreements,
technological innovations, or new commercial products by the Company,
collaborative partners or competitors, changes in government regulation,
regulatory actions, changes in patent laws, developments concerning proprietary
rights, quarterly variations in operating results, litigation and other events
may have a significant impact on the market price of the Company's Common Stock.
The stock market has from time to time experienced significant price and volume
fluctuations which have particularly affected the market prices of the stocks of
technology companies, and which may be unrelated to the operating performance of
particular companies. Further, there has been particular volatility in the
market prices of securities of biotechnology and other life sciences companies.
 
RISKS AND UNCERTAINTIES REGARDING FORWARD-LOOKING STATEMENTS
 
    All statements in this Prospectus that are not historical are
forward-looking statements that are subject to certain risks and uncertainties.
Such statements are based on management's current expectations and are subject
to a number of factors and uncertainties that could cause actual results to
differ
 
                                       20
<PAGE>
materially from those described in the forward-looking statements. The Company
cautions investors that there can be no assurance that actual results or
business conditions will not differ materially from those projected or suggested
in such forward-looking statements as a result of various factors, including,
but not limited to, the following: risks associated with market acceptance of
the Company's technology and products; technological change; risks associated
with the Company's expansion of operations, management growth, and dependence on
key personnel; intense competition; the variation in the Company's operating
results; the Company's ability to develop and protect proprietary products and
technologies and to enter into collaborative commercial relationships; the
Company's future capital requirements; and uncertainties as to the extent of
future government regulation of the Company's business. As a result, the
Company's future development efforts involve a high degree of risk.
 
                                       21
<PAGE>
                                USE OF PROCEEDS
 
    The net proceeds to the Company from the sale of shares of Common Stock
offered by the Company are estimated to be approximately $58.7 million
(approximately $67.5 million if the Underwriters' over-allotment options are
exercised in full), based on an assumed offering price of $41.625 per share,
less underwriting discounts and commissions and estimated expenses payable by
the Company.
 
    The Company expects to use approximately $30.0 million of the net proceeds
of the Offerings for capital expenditures to scale up manufacturing capacity,
expand facilities for research and development, and for laboratory equipment and
information systems. The Company has not yet identified the specific amounts and
uses of approximately $28.7 million (approximately 49%) of the net proceeds. The
Company's Board of Directors and management will retain broad discretion as to
the allocation of the net proceeds of the Offerings.
 
    The amounts actually expended for each purpose and the timing of such
expenditures will depend upon numerous factors, including payments received
under existing and possible future collaborative agreements; the availability of
government research grant payments; the progress of the Company's collaborative
and independent research and development projects; the costs of preclinical and
clinical trials for the Company's products; the prosecution, defense and
enforcement of patent claims and other intellectual property rights; and the
development of manufacturing, marketing and sales capabilities. Pending such
uses, the Company intends to invest the net proceeds of the Offerings in
short-term, investment-grade, interest-bearing securities.
 
                                       22
<PAGE>
                          PRICE RANGE OF COMMON STOCK
 
    Affymetrix' Common Stock has been traded on the Nasdaq National Market under
the symbol "AFFX" since Affymetrix' initial public offering on June 6, 1996.
Prior to that time, there was no public
market for Affymetrix' Common Stock. On October 16, 1997 the closing price of
the Common Stock reported on the Nasdaq National Market was $41.625 per share.
As of October 16, 1997, the number of shareholders of record of Affymetrix'
Common Stock was 342.
 
    The high and low sales prices as reported on the Nasdaq National Market
during each of the quarters since Affymetrix' Common Stock became publicly
traded are set forth below:
 
<TABLE>
<CAPTION>
                                                                                                LOW       HIGH
                                                                                             ---------  ---------
<S>                                                                                          <C>        <C>
1996
Second Quarter (beginning June 6, 1996)....................................................  $  14.500  $  17.875
Third Quarter..............................................................................      9.000     19.000
Fourth Quarter.............................................................................     15.875     23.500
</TABLE>
 
<TABLE>
<CAPTION>
                                                                                                LOW       HIGH
                                                                                             ---------  ---------
<S>                                                                                          <C>        <C>
1997
First Quarter..............................................................................  $  19.750  $  36.375
Second Quarter.............................................................................     20.375     35.250
Third Quarter..............................................................................     29.125     49.875
Fourth Quarter (through October 16, 1997)..................................................     41.250     47.625
</TABLE>
 
                                DIVIDEND POLICY
 
    The Company has not paid any cash dividends on its Common Stock during the
last five fiscal years. The Company currently intends to retain any earnings for
use in its business and does not anticipate paying any cash dividends in the
foreseeable future.
 
                                       23
<PAGE>
                                 CAPITALIZATION
 
    The following table sets forth the capitalization of the Company (i) as of
June 30, 1997 and (ii) as adjusted to reflect the receipt of the estimated net
proceeds from the sale of the 1,500,000 shares of Common Stock offered by the
Company, at an assumed public offering price of $41.625 per share, after
deducting the underwriting discounts and commissions and estimated offering
expenses payable by the Company. This table should be read in conjunction with
the financial statements of the Company and the notes thereto included elsewhere
in this Prospectus.
 
<TABLE>
<CAPTION>
                                                                                         JUNE 30, 1997
                                                                                   --------------------------
                                                                                      ACTUAL       ADJUSTED
                                                                                   ------------  ------------
                                                                                         (IN THOUSANDS)
<S>                                                                                <C>           <C>
Noncurrent portion of capital lease obligation(1)................................  $        619  $        619
Shareholders' equity:
  Preferred stock; no par value, 27,500,000 shares authorized; no shares issued
    and outstanding..............................................................            --            --
  Common stock; no par value, 50,000,000 shares authorized; 22,623,987 shares
    issued and outstanding, 24,123,987 shares issued and outstanding, as
    adjusted(2)..................................................................       158,750       217,410
  Notes receivable from officers.................................................           (41)          (41)
  Unrealized gain on available-for-sale securities...............................            15            15
  Deferred compensation..........................................................        (1,087)       (1,087)
  Accumulated deficit............................................................       (54,875)      (54,875)
                                                                                   ------------  ------------
    Total shareholders' equity...................................................       102,762       161,422
                                                                                   ------------  ------------
      Total capitalization.......................................................  $    103,381  $    162,041
                                                                                   ------------  ------------
                                                                                   ------------  ------------
</TABLE>
 
- --------------
 
(1) See Note 6 of Notes to Financial Statements for a description of the
    Company's obligation under a capital lease.
 
(2) Excludes (i) 203,881 shares of Common Stock issuable upon exercise of
    outstanding warrants at an exercise price of $8.25 per share, (ii) 2,920,783
    shares issuable upon exercise of outstanding options at September 30, 1997,
    at a weighted average price of $9.89 per share and (iii) 1,426,341 shares of
    Common Stock reserved for future issuance under the Stock Plans. See Note 7
    of Notes to Financial Statements.
 
                                       24
<PAGE>
                                    DILUTION
 
    The net tangible book value of the Company as of June 30, 1997 was $102.8
million or approximately $4.54 per share. Net tangible book value per share
represents the amount of the Company's total tangible assets less total
liabilities, divided by the number of shares of Common Stock outstanding at June
30, 1997. After giving effect to the estimated net proceeds from the sale by the
Company of the 1,500,000 shares of Common Stock offered in the Offerings at an
assumed public offering price of $41.625 per share, and deducting the
underwriting discounts and commissions and estimated offering expenses payable
by the Company, the pro forma net tangible book value of the Company as of June
30, 1997 would have been $161.4 million or approximately $6.69 per share of
Common Stock. This represents an immediate increase in net tangible book value
of $2.15 per share to existing shareholders and an immediate dilution in pro
forma net tangible book value of $34.94 per share to purchasers of Common Stock
in the Offerings. The following table illustrates this per share dilution:
 
<TABLE>
<CAPTION>
Assumed public offering price..............................................             $   41.63
<S>                                                                          <C>        <C>
  Pro forma net tangible book value as of June 30, 1997....................       4.54
  Increase attributable to new investors...................................       2.15
                                                                             ---------
Pro forma net tangible book value after the Offerings......................                  6.69
                                                                                        ---------
Dilution to new investors..................................................             $   34.94
                                                                                        ---------
                                                                                        ---------
</TABLE>
 
                                       25
<PAGE>
                            SELECTED FINANCIAL DATA
 
    The selected statement of operations data set forth below for each of the
three years in the period ended December 31, 1996, and the balance sheet data at
December 31, 1995 and 1996 are derived from the financial statements which have
been audited by Ernst & Young LLP, independent auditors, that are included
elsewhere in this Prospectus and are qualified by reference to such Financial
Statements and Notes related thereto. The selected statement of operations data
for the years ended December 31, 1992 and 1993 and the selected balance sheet
data at December 31, 1992, 1993 and 1994 have been derived from the audited
financial statements of the Company audited by Ernst & Young LLP, independent
auditors, that are not included or incorporated by reference herein. The
selected statement of operations data for the six months ended June 30, 1996 and
1997 and the selected balance sheet data as of June 30, 1997 are derived from
unaudited financial statements included elsewhere in this Prospectus. The
unaudited financial statements include all normal recurring adjustments that the
Company considers necessary for the fair presentation of financial position and
results of operations for these interim periods. Operating results for the six
months ended June 30, 1997 are not necessarily indicative of the results that
may be expected for the entire year ending December 31, 1997. The table should
be read in conjunction with "Management's Discussion and Analysis of Financial
Condition and Results of Operations" and the Financial Statements and the Notes
related thereto included elsewhere herein.
 
<TABLE>
<CAPTION>
                                                                                                               SIX MONTHS
                                                                  YEAR ENDED DECEMBER 31,                    ENDED JUNE 30,
                                                   -----------------------------------------------------  --------------------
                                                     1992       1993       1994       1995       1996       1996       1997
                                                   ---------  ---------  ---------  ---------  ---------  ---------  ---------
                                                                   (IN THOUSANDS, EXCEPT PER SHARE DATA)      (UNAUDITED)
<S>                                                <C>        <C>        <C>        <C>        <C>        <C>        <C>
STATEMENT OF OPERATIONS DATA:
Revenue:
  Product........................................  $      --  $      --  $      --  $      --  $   1,389  $     457  $   1,362
  Contract and grant.............................         43      1,413      1,574      4,625     10,583      3,258      6,188
                                                   ---------  ---------  ---------  ---------  ---------  ---------  ---------
    Total revenue................................         43      1,413      1,574      4,625     11,972      3,715      7,550
Costs and expenses:
  Cost of product revenue........................         --         --         --         --      2,178        707      1,844
  Research and development.......................      4,106      6,566      9,483     12,420     18,762      8,310     12,710
  General and administrative.....................        582        577      2,303      3,833      7,569      3,550      5,815
                                                   ---------  ---------  ---------  ---------  ---------  ---------  ---------
      Total costs and expenses...................      4,688      7,143     11,786     16,253     28,509     12,567     20,369
                                                   ---------  ---------  ---------  ---------  ---------  ---------  ---------
Loss from operations.............................     (4,645)    (5,730)   (10,212)   (11,628)   (16,537)    (8,852)   (12,819)
Interest income (expense), net...................        (15)       138        532        881      4,310      1,154      2,687
                                                   ---------  ---------  ---------  ---------  ---------  ---------  ---------
Net loss.........................................  $  (4,660) $  (5,592) $  (9,680) $ (10,747) $ (12,227) $  (7,698) $ (10,132)
                                                   ---------  ---------  ---------  ---------  ---------  ---------  ---------
                                                   ---------  ---------  ---------  ---------  ---------  ---------  ---------
Historical net loss per share....................                                                                    $   (0.45)
                                                                                                                     ---------
                                                                                                                     ---------
Shares used in computing historical net loss per
 share...........................................                                                                       22,594
Pro forma net loss per share(1)..................             $   (0.52) $   (0.55) $   (0.61) $   (0.61) $   (0.43)
                                                              ---------  ---------  ---------  ---------  ---------
                                                              ---------  ---------  ---------  ---------  ---------
Shares used in computing pro forma net loss per
 share(1)........................................                10,715     17,653     17,664     20,131     17,782
</TABLE>
 
<TABLE>
<CAPTION>
                                                                             DECEMBER 31,
                                                        ------------------------------------------------------
                                                          1992       1993       1994       1995        1996
                                                        ---------  ---------  ---------  ---------  ----------
                                                                                                                 JUNE 30,
                                                                                                                -----------
                                                                                                                   1997
                                                                                                                -----------
                                                                                  (IN THOUSANDS)                (UNAUDITED)
<S>                                                     <C>        <C>        <C>        <C>        <C>         <C>
BALANCE SHEET DATA:
Cash, cash equivalents, and short-term investments....  $      94  $  20,392  $  17,805  $  38,883  $  108,982   $  94,645
Working capital.......................................       (320)    17,452     15,677     36,070     107,668      93,437
Total assets..........................................        813     22,817     19,861     44,552     118,860     111,500
Long-term obligations.................................        564         --      7,135        948         741         619
Accumulated deficit...................................     (6,497)   (12,089)   (21,769)   (32,516)    (44,743)    (54,875)
Total shareholders' equity (net capital deficiency)...       (181)    19,214      9,170     38,519     112,493     102,762
</TABLE>
 
- --------------
 
(1) See Note 2 of Notes to Financial Statements for an explanation of the
    determination of the number of shares used in computing pro forma net loss
    per share.
 
                                       26
<PAGE>
                    MANAGEMENT'S DISCUSSION AND ANALYSIS OF
                 FINANCIAL CONDITION AND RESULTS OF OPERATIONS
 
    The following Management's Discussion and Analysis of Financial Condition
and Results of Operations contains forward-looking statements, such as financial
projections, information and expectations about the Company's products and
markets, which involve risks and uncertainties. The Company's actual results
could differ materially from those anticipated in these forward-looking
statements, as a result of certain factors, including those set forth under the
heading "Risk Factors" and elsewhere herein.
 
OVERVIEW
 
    Affymetrix has developed and intends to establish its GeneChip system as the
platform of choice for acquiring, analyzing and managing complex genetic
information. The business and operations of Affymetrix were commenced in 1991 by
Affymax N.V. ("Affymax") and were initially conducted within Affymax. In March
1992, Affymetrix was incorporated as a California corporation and became a
wholly-owned subsidiary of Affymax. Beginning in September 1993, Affymetrix
issued equity securities which diluted Affymax' shareholding in Affymetrix. In
March 1995, Glaxo purchased Affymax, including its then 65% interest in
Affymetrix. Glaxo's ownership of Affymetrix at September 30, 1997 was
approximately 33%.
 
    To date, Affymetrix has placed 38 of its GeneChip systems for research use.
The Company began shipments of its products for genetic analysis of HIV in April
1996 and for the p53 tumor suppressor gene in July 1997. Payments received for
certain systems prior to April 1996 were recorded as contract revenues pursuant
to development agreements. Failure of the Company to successfully develop,
manufacture and market additional products or to realize product revenues would
have a material adverse effect on the Company's business, financial condition
and results of operations.
 
    The Company has incurred operating losses in each year since its inception,
including a net loss of approximately $12.2 million during the year ended
December 31, 1996 and $10.1 million for the six months ended June 30, 1997. At
June 30, 1997, the Company had an accumulated deficit of approximately $54.9
million. The Company's losses have resulted principally from costs incurred in
research and development and from general and administrative costs associated
with the Company's operations. These costs have exceeded the Company's interest
income and revenues, which to date have been generated principally from
collaborative research and development agreements, government research grants,
cash and short-term investments. The Company expects to incur substantial
additional operating losses over the next several years as a result of increases
in its expenses for research and product development, manufacturing scale up,
expanding sales and marketing and depreciation from capital expenditures.
 
RESULTS OF OPERATIONS
 
  SIX MONTHS ENDED JUNE 30, 1997 AND JUNE 30, 1996
 
    PRODUCT REVENUE.  Product revenue was $1.4 million for the six months ended
June 30, 1997. In April 1996, Affymetrix commenced commercial sales of the
GeneChip system and an HIV probe array for research use. Product revenue of
$457,000 was recognized for the six months ended June 30, 1996.
 
    CONTRACT AND GRANT REVENUE.  Contract and grant revenue was $6.2 million for
the six months ended June 30, 1997 compared to $3.3 million for the six months
ended June 30, 1996. The increase was primarily due to milestone accomplishments
with certain collaborative partners and increases in funding from the ATP and
NIH grants.
 
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    COST OF PRODUCT REVENUE.  Cost of product revenue was $1.8 million for the
six months ended June 30, 1997 compared to $707,000 for the six months ended
June 30, 1996. Margins fluctuated during the six month periods due primarily to
scale-up costs of production.
 
    RESEARCH AND DEVELOPMENT.  Research and development expenses were $12.7
million for the six months ended June 30, 1997 compared to $8.3 million for the
same period ending June 30, 1996. The increase in research and development
expenses was attributable primarily to the hiring of additional research and
development personnel and associated purchases of research supplies. The Company
expects research and development spending to increase over the next several
years as product development and core research efforts continue to expand.
 
    GENERAL AND ADMINISTRATIVE EXPENSES.  General and administrative expenses
were $5.8 million for the six months ended June 30, 1997 compared to $3.6
million for the six months ended June 30, 1996. The increase in general and
administrative expenses was attributable primarily to the hiring of additional
management personnel, professional fees (primarily legal fees) and overall
scale-up of the Company's operations and business development efforts. General
and administrative expenses are expected to continue to increase as the Company
expands sales and marketing and adds management and support staff.
 
    NET INTEREST INCOME.  Net interest income was $2.7 million for the six
months ended June 30, 1997. This compares to net interest income of $1.2 million
for the six months ended June 30, 1996. The increase in net interest income was
primarily attributable to increased investment balances from the initial public
offering in June 1996.
 
  YEARS ENDED DECEMBER 31, 1996 AND DECEMBER 31, 1995
 
    PRODUCT REVENUE.  In April 1996, Affymetrix commenced commercial sales of
the GeneChip system and an HIV probe array for research use. Product revenue of
$1.4 million and costs of product revenue of $2.2 million were recognized in the
last nine months of 1996 as a result.
 
    CONTRACT AND GRANT REVENUE.  Contract and grant revenue was $10.6 million
for 1996 compared to $4.6 million for 1995. The increase was primarily a result
of its ATP grant, NIH grant and revenue earned from collaborative agreements
with Genetics Institute, HP and bioMerieux.
 
    RESEARCH AND DEVELOPMENT.  Research and development expenses were $18.8
million for 1996 compared to $12.4 million for 1995. The increase in research
and development expenses was attributable primarily to the hiring of additional
research and development personnel, costs incurred to further product
development and increased purchases of research supplies.
 
    GENERAL AND ADMINISTRATIVE EXPENSES.  General and administrative expenses
were $7.6 million in 1996 compared to $3.8 million for 1995. The increase in
general and administrative expenses was attributable primarily to the hiring of
additional management personnel and the incurring of legal and other
professional fees in connection with the overall scale-up of operations and
business development efforts.
 
    INTEREST INCOME.  Interest income was $4.4 million for 1996 compared to $1.3
million for 1995. The increase resulted from the investment of net proceeds from
Affymetrix' private placement of Series B Senior Convertible Preferred Stock in
August 1995 and net proceeds from its initial public offering in June 1996.
Interest expense decreased to $106,000 for 1996 from $420,000 in 1995 as a
result of the conversion of a $6.0 million subordinated convertible promissory
note held by Affymax in August 1995.
 
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  YEARS ENDED DECEMBER 31, 1995 AND DECEMBER 31, 1994
 
    CONTRACT AND GRANT REVENUE.  Contract and grant revenue was $4.6 million for
1995 compared to $1.6 million for 1994. The increase was primarily as a result
of the Company's ATP grant and revenue earned from collaborative agreements with
Genetics Institute and HP.
 
    RESEARCH AND DEVELOPMENT.  Research and development expenses were $12.4
million for 1995 compared to $9.5 million for 1994. The increase in research and
development expenses was attributable primarily to the hiring of additional
research and development personnel, costs incurred to establish a pilot
manufacturing facility, and increased purchases of research supplies.
 
    GENERAL AND ADMINISTRATIVE EXPENSES.  General and administrative expenses
were $3.8 million for 1995 compared to $2.3 million for 1994. The increase in
general and administrative expenses was attributable primarily to the hiring of
additional management personnel and the incurring of legal and other
professional fees in connection with the overall scale-up of operations and
business development efforts.
 
    INTEREST INCOME.  Interest income was $1.3 million for 1995 compared to
$575,000 for 1994. The increase resulted from the investment of net proceeds
from Affymetrix' private placement of Series B Senior Convertible Preferred
Stock in August 1995. Interest expense resulted from lease financing for
manufacturing equipment and facilities.
 
LIQUIDITY AND CAPITAL RESOURCES
 
    The Company has financed its operations primarily through the sale of equity
securities, contributions from Affymax, government grants, collaborative
agreements, and interest income. Proceeds raised through the sale of equity
securities include net proceeds of $85.1 million from its initial public
offering in June 1996 and aggregate net proceeds of $53.6 million from private
placements in August 1995 and September 1993.
 
    As of June 30, 1997, the Company's cash, cash equivalents and short-term
investments were $94.6 million compared to $109.0 million at December 31, 1996.
The decrease is primarily attributable to expansion of core research,
manufacturing and capital spending, and growth in general and administrative
expenses. Net cash used in operating activities was $9.6 million in the first
six months of 1997, $11.8 million in 1996, $10.2 million in 1995 and $7.4
million in 1994. The cash used for operations was primarily to fund research and
development expenses and manufacturing start-up costs related to the
introduction and support of Affymetrix' products.
 
    In the first six months of 1997, $30.1 million was provided by investing
activities. Net cash used by the Company in investing activities was $61.6
million in 1996 and $26.7 million in 1995. In 1994, $1.1 million in cash was
provided by investing activities. Capital expenditures totaled $4.4 million in
the first six months of 1997, $3.5 million in 1996, $2.3 million in 1995 and
$1.2 million in 1994. Purchases of available-for-sale securities were $44.1
million, $149.4 million, $38.4 million and $3.0 million for the first six months
of 1997 and in 1996, 1995 and 1994, respectively. Proceeds from sales and
maturities of available-for-sale securities were $78.6 million, $91.3 million,
$14.0 million and $5.3 million for the first six months of 1997 and in 1996,
1995 and 1994, respectively.
 
    Net cash provided by financing activities of $85.0 million in 1996, $32.7
million in 1995 and $6.5 million in 1994 are primarily the result of public and
private placements of securities, contributions from Affymax and equipment lease
financing.
 
    The Company anticipates that its existing capital resources, together with
the net proceeds of the Offerings and interest earned thereon, will enable it to
maintain currently planned operations through at least the end of 2000. However,
this expectation is based on the Company's current operating plan,
 
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<PAGE>
which could change, and therefore the Company could require additional funding
sooner than anticipated. In addition, the Company expects its capital
requirements to increase over the next several years as it expands its
facilities and acquires scientific equipment to support expanded manufacturing
and research and development efforts. The Company's long-term capital
expenditure requirements will depend on numerous factors, including: the
progress of its research and development programs; initiation or expansion of
research programs; the development of commercial scale manufacturing
capabilities; its ability to maintain existing collaborative and customer
arrangements and establish and maintain new collaborative and customer
arrangements; the costs involved in preparing, filing, prosecuting, defending
and enforcing intellectual property rights; the effectiveness of product
commercialization activities and arrangements; and other factors.
 
    As of December 31, 1996, Affymetrix has net operating loss carryforwards for
income tax purposes of approximately $31.0 million which will expire at various
dates beginning in 2008 through 2011, if not utilized. Because Affymetrix has
experienced ownership changes, future utilization of these carryforwards may be
subject to certain limitations as defined by Internal Revenue Code and similar
state regulations. As a result of the annual limitation, a portion of these
carryforwards may expire before ultimately becoming available to reduce income
tax liabilities.
 
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<PAGE>
                                    BUSINESS
 
OVERVIEW
 
    Affymetrix is recognized as a worldwide leader in the field of DNA chip
technology. The Company has developed and intends to establish its GeneChip
system as the platform of choice for acquiring, analyzing and managing complex
genetic information in order to improve the diagnosis, monitoring and treatment
of disease. The Company's GeneChip system consists of disposable DNA probe
arrays containing gene sequences on a chip, a scanner and other instruments to
process the probe arrays, and software to analyze and manage genetic information
from the probe arrays. The Company commenced commercial sales of the GeneChip
system for research use in April 1996 and currently sells its products to
pharmaceutical and biotechnology companies, academic research centers and
clinical reference laboratories.
 
RECENT DEVELOPMENTS
 
    GENECHIP TECHNOLOGY PLATFORM ESTABLISHED.  To date, Affymetrix has placed 38
GeneChip systems for research use. A second generation scanner, manufactured by
HP, was introduced in April 1997.
 
    MANUFACTURING INFRASTRUCTURE OPERATIONAL.  The Company's Sunnyvale,
California plant, currently capable of producing 80,000 GeneChip probe arrays
per year, is being expanded.
 
    INTELLECTUAL PROPERTY POSITION STRENGTHENED.  The Company has been issued 27
United States patents and 78 patent applications are pending. The Company has
also licensed rights to important patents related to genetic information and
technologies.
 
    GENOMICS CUSTOMER BASE ESTABLISHED.  Customers include Genetics Institute,
Inc. ("Genetics Institute"), Glaxo, Hoechst Marion Roussel, Inc. ("Hoechst"),
Merck & Co., Inc. ("Merck"), the Parke-Davis division of Warner-Lambert Company
("Parke-Davis"), Pfizer Inc. ("Pfizer") and Pioneer Hi-Bred International, Inc.
("Pioneer Hi-Bred"). In August 1997, F. Hoffmann-La Roche Ltd. ("Roche") became
the Company's first EasyAccess-TM- customer.
 
    DISEASE MANAGEMENT GENECHIP PRODUCTS COMMERCIALIZED.  The Company began
shipments of its products for genetic analysis of HIV in April 1996 and for the
p53 tumor suppressor gene in July 1997.Affymetrix has established collaborations
with bioMerieux, Glaxo and OncorMed in bacteriology, virology, and oncology,
respectively.
 
    POLYMORPHISM DISCOVERY AND DATABASE PROJECT INITIATED.  Internal and
collaborative efforts have identified nearly 2,000 genetic markers. Affymetrix
entered into a consortium with Bristol-Myers and Millennium to fund research at
the Whitehead Institute to identify novel genetic markers and study their role
in disease.
 
BACKGROUND
 
  GENES AND DISEASE
 
    The entire genetic content of an organism is known as its genome. DNA is the
molecule that makes up genes and encodes the genetic instructions. These
instructions are embodied in the sequence of the four nucleotide bases (A, C, G
and T) that are the chemical building blocks of DNA. The DNA molecule is a
combination of two strands held together by chemical bonds between nucleotide
bases on one strand and the bases on the other strand. Only certain pairs of
nucleotide bases can form these bonds: C always pairs with G, and A always pairs
with T. Such paired DNA strands are said to be complementary. When two DNA
strands are complementary, they can bind together to form a double helix in a
process
 
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<PAGE>
called hybridization. The Company's GeneChip technology relies on this principle
of hybridization to analyze complex genetic information.
 
    Cells carry out their normal biological functions through the genetic
instructions encoded in their DNA. This genetic process, known as gene
expression, involves several steps. In the first step, nucleotides in a gene are
copied into a related nucleic acid molecule called messenger RNA. Messenger RNA
instructs the cell to produce proteins. Proteins are molecules that regulate or
perform most of the physiological functions of the body. Because the order of
nucleotides in each gene is different, each gene directs the production of a
different protein. An organism's characteristics are thus ultimately determined
by proteins encoded by its DNA.
 
    Increased awareness of the role of genes in regulating the functions of
living organisms has generated a worldwide effort to identify and sequence genes
of many organisms, including the estimated three billion nucleotide pairs and
100,000 genes within the human genome. This effort is being led by the Human
Genome Project and related academic, government and industry research projects.
Once the genes and their nucleotide sequences are identified, it is anticipated
that many years of additional research will be required to understand the
specific function and role in disease of each of these genes. This research,
commonly referred to as genomics, is expected to lead to a new health care
paradigm where disease is understood at the molecular level, allowing patients
to be diagnosed according to their genetic profile and then treated with drugs
designed to work on specific molecular targets.
 
  GENETIC VARIABILITY
 
    The diversity of living organisms results from variability in their genomes.
Variability stems from differences in the sequences of genes and from
differences in levels of gene expression. In order to understand how mutations
in particular genes cause disease, scientists must compare both sequence and
expression patterns of genes from healthy and diseased individuals. Currently,
these efforts are laborious, time consuming and expensive, requiring the
repeated sequencing of the same genes from a large number of persons. The
Company believes that its GeneChip technology will simplify, accelerate and
reduce the cost of analyzing genetic variability (both sequence and expression)
and lead to new opportunities in disease management.
 
    SEQUENCE VARIABILITY.  Changes in the sequences of normal genes may be
introduced by environmental or other factors, such as errors in replication of
genes. These changes are known as polymorphisms, and the affected genes can be
passed from generation to generation. In some cases, polymorphisms have no
effect on the biology of the organism. However, in other cases, polymorphisms
can result in the altered function or expression of the protein encoded by the
gene. Such polymorphisms are called mutations. Mutations in single genes have
been associated with diseases such as cystic fibrosis, and mutations in multiple
genes have been associated with diseases such as cancer and diabetes. By
screening for polymorphisms, researchers seek to correlate variability in the
sequence of genes with a specific disease. By sequencing a gene of interest from
a large number of healthy and diseased persons, researchers are able to
correlate specific gene mutations with the disease. A typical polymorphism
screening project on one disease might require sequencing 100 genes of 3,000
nucleotide bases each in up to 500 patients, or a total of 150 million bases.
Currently, the polymorphism screening process uses gel-based sequencing which
cannot efficiently correlate polymorphisms with human disease due to the time
and cost required. In contrast, the Company believes that its GeneChip
technology is a sufficiently powerful tool to identify sequence variations and
has initiated a large scale polymorphism discovery and database project to
identify these correlations.
 
                                       32
<PAGE>
    EXPRESSION VARIABILITY.  The genes expressed in a given cell, as well as the
timing and levels of their expression, are another basis for genetic
variability. Although most cells contain an organism's full set of genes, each
cell expresses only a small fraction of this set in different quantities and at
different times. The expression of the wrong or defective genes, or the
overexpression or underexpression of normal genes have been associated with
human diseases, as well as treatment failures in specific patient populations.
By identifying genes that are differentially expressed in particular diseases or
patient populations, new targets can be identified for which new therapies can
then be developed. Expression monitoring may also help demonstrate the likely
effectiveness of new as well as existing therapeutic agents and lead to the
development of new therapeutics and diagnostic tools. The effectiveness of
monitoring gene expression is a function of the quality of the cell population
being studied, the number of genes that can be monitored simultaneously, the
sensitivity of the method (ability to measure small changes or low levels of
gene expression) and the ability of the method used to provide quantitative
information. Relative levels of gene expression are currently monitored
primarily through a costly and time-consuming process of sequencing many copies
of each gene.
 
OPPORTUNITIES ARISING FROM GENETIC VARIABILITY
 
    The analysis of genetic variability in organisms is revealing polymorphisms
and differences in gene expression levels that correlate with diseases,
prognoses for those diseases, and likely therapeutic outcomes. These variations
provide new opportunities for therapeutic intervention that can be more
efficacious and have fewer side effects than drugs that affect larger portions
of one or more biological pathways. The Company believes that by providing a
powerful tool to identify appropriate pathways for therapeutic intervention,
evaluate lead compounds and assess the efficacy and toxicology of these
compounds on biological systems, the GeneChip system can facilitate the drug
discovery process.
 
    In addition to revealing opportunities for the discovery and development of
new therapeutics, the understanding of sequence and expression variability in
organisms may have the potential to effect a major paradigm shift in disease
management and the diagnostics industry. This highly competitive industry is
characterized by low margins and large barriers to entry, with substantial
pressure to reduce prices exerted by health care providers. Further, information
available from many current diagnostics tests often provides insufficient
information as to the etiology, prognosis, and potential treatment options for a
particular clinical presentation.
 
    Access to complex genetic information, such as changes in gene sequences or
expression levels that have previously been correlated with particular outcomes,
has the potential to provide guidance on appropriate therapeutic regimens. The
value of this information in reducing total health care costs and improving the
quality of life is very high. For example, by determining that a HIV-infected
patient on a triple drug combination therapy is resistant to all three drugs,
the health care provider can change the therapeutic regimen to include drugs to
which the patient is not resistant and thereby reduce or prevent hospitalization
costs.
 
    The use of complex genetic information to manage disease is in its infancy.
Current techniques for gathering complex genetic information are time-consuming,
require skilled labor, and can analyze only limited lengths of contiguous DNA
sequences in a given run. This has prevented any systematic study of how
sequence variability and expression variability correlate with particular
disease outcomes. The Company believes that new technology, such as the
Company's GeneChip system, will be required to utilize complex genetic
information in health care.
 
BUSINESS STRATEGY
 
    Affymetrix' strategy is to capitalize on its leadership position in the DNA
probe array field by applying its GeneChip technology primarily to genomics,
disease management and polymorphism discovery. The Company intends to
commercialize its GeneChip probe array technology for sale to pharmaceutical
 
                                       33
<PAGE>
and biotechnology companies, academic research centers and clinical reference
laboratories by demonstrating its advantages over conventional tools used for
DNA sequence and expression monitoring analysis. The Company offers both custom
and standard configurations of its GeneChip probe arrays to customers under a
variety of access plans tailored to meet customer needs, such as the high-volume
EasyAccess program subscribed to by Roche. In addition, the Company will
continue to enter into collaborations to expand the utilization and applications
of its GeneChip technology. The Company generally structures collaborations to
generate research funding and probe array sales, as well as earn future
milestone and royalty payments on sales of drugs or other products developed
using its GeneChip technology.
 
APPLICATIONS
 
    Currently, there are three principal applications of the Company's
technology: genomics, disease management and polymorphism discovery.
 
  GENOMICS
 
    Genomics is the study of genes and their functions. A fundamental objective
of this research is to link gene function with disease. Gene expression
monitoring is a valuable tool for identifying these correlations. To facilitate
the monitoring of gene expression, the Company designs and manufactures probe
arrays with DNA probes that are complementary to sequences within a gene of
interest. By synthesizing specific probes for multiple genes on a single probe
array, the Company enables researchers to quickly, quantitatively and
simultaneously monitor the expression of a large number of genes of interest. By
monitoring the expression of such genes at different times, researchers can use
the probe arrays to understand the relationship between gene expression and
disease progression in particular patient populations. The Company believes that
such information will be an important tool in the understanding of gene function
and the development of new disease management tools.
 
    The Company is currently selling expression monitoring GeneChip arrays, each
capable of analyzing more than 1,600 human, mouse or yeast genes. Affymetrix is
also developing next generation probe arrays that monitor the expression of
7,500 or more genes per probe array. For example, a 7,500 gene probe array is
being designed to monitor the expression of all of the human genes for which
full length sequences are currently in public databases.
 
    Affymetrix intends to commercialize the expression monitoring applications
of its GeneChip technology for use in identifying and validating novel targets
for drug discovery broadly for sale to pharmaceutical, biotechnology, academic
research organizations and clinical reference laboratories. The Company is
offering different access plans to its technology centered around a pricing
model that is based on the number of data points and value of the gene
collections being monitored on a particular GeneChip probe array. Actual pricing
of the GeneChip expression probe arrays under this model depends on a number of
additional factors, including the magnitude of the customer's research effort,
whether the genes being monitored are human or from other organisms, whether
intellectual property is to be retained, shared or disclosed and whether the
Company provides custom chip design or screening services to a customer and the
amount of any up-front fees, milestones, royalties or other payments to be
received by the Company. For example, the Company's largest supply arrangement
to date is with Roche, pursuant to which Roche has gained broad access to the
Company's gene expression probe arrays under the EasyAccess plan designed to
incent high-volume use.
 
    To date, the Company has more than a dozen commercial customers for its
GeneChip expression probe arrays, including Genetics Institute, Glaxo, Hoechst,
Merck, Parke-Davis, Pfizer, Pioneer Hi-Bred, and Roche. In addition, the Company
has entered into an alliance with Incyte, pursuant to which the companies are
jointly developing and marketing specific databases, probe arrays and services
under the LifeChip-TM- trademark.
 
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<PAGE>
  DISEASE MANAGEMENT
 
    Disease management is an emerging field that seeks to improve the
effectiveness of health care by collecting information on patients from the time
of diagnosis to the end of therapy and subsequently measuring the outcomes of
various treatment protocols. Affymetrix believes that a core component of
disease management will be the ability to monitor gene expression and provide
sequence information from genes implicated in disease. The Company has therefore
developed GeneChip assays for this purpose and believes that such assays will
facilitate more efficient and effective patient management. The Company is
focusing on the development and commercialization of disease management products
in infectious diseases, cancer and other areas, including drug metabolism.
 
    Affymetrix has established partnerships and customer relationships with
leading diagnostic companies, clinical reference laboratories and medical
research centers to further its disease management strategy. To date, the
Company has introduced two disease management GeneChip assays for the research
and clinical reference markets: the HIV and p53 GeneChip products. These
products provide sequence information from the reverse transcriptase and
protease genes of HIV and the p53 tumor suppressor gene, respectively. The
Company is working with commercial and academic researchers to correlate
specific mutations in these genes with therapeutic outcomes. In the case of HIV,
the Company has entered into a collaboration with Glaxo, a world leader in sales
of HIV antivirals, to develop a database correlating patient outcomes under
varied therapeutic drug regimens with specific mutations in the HIV virus. In
oncology, the Company has a collaboration with OncorMed, a leader in the genetic
testing reference laboratory business. In bacteriology, the Company has formed a
collaboration with bioMerieux, a world leader in providing bacterial
identification and antibiotic resistance testing.
 
    Affymetrix believes that before its GeneChip probe arrays can become widely
used tools in disease management, significant additional research including
clinical trials supporting FDA registration may be required. Furthermore,
additional instrumentation and automation will need to be developed to allow for
the handling of the large volumes of testing anticipated in the clinical
diagnostic setting. bioMerieux is developing such instrumentation as part of its
collaboration with the Company. Affymetrix is also seeking to partner with, or
license technology to, other established diagnostic companies to develop, seek
regulatory approval, and commercialize probe arrays and instrumentation for
broader clinical use.
 
  POLYMORPHISM DISCOVERY
 
    As genes in the human genome are identified, sequenced and mapped, the value
of understanding the variability of sequences in these genes increases.
Researchers must determine the normal sequence of the gene, which mutations
exist and whether these mutations correlate with a disease. This currently
requires the sequencing of samples from a large number of affected and
unaffected individuals. Furthermore, during clinical trials, the Company
believes that pharmacogenomics (the understanding of the impact that genetic
variation has on therapeutic effectiveness and toxicity) will be increasingly
important. Using sequence checking strategies developed by the Company,
Affymetrix believes that its GeneChip probe arrays could significantly reduce
the cost and time of polymorphism screening, which is currently achieved through
more labor intensive gel-based sequencing techniques.
 
    Affymetrix has recently initiated a major resequencing effort aimed at
discovering the most common polymorphisms implicated in prevalent diseases.
Through a number of customized applications of its GeneChip technology, the
Company believes it is uniquely positioned both to identify a large number of
polymorphisms and to detect their presence across broad populations to link this
genetic variation to disease. These customized applications may provide rapid
analysis of (i) genetic markers, (ii) selected candidate genes potentially
implicated in disease, (iii) genes associated with toxic drug reactions and (iv)
genes that are existing drug targets. As these efforts are advanced and the
variability of these genes is stored in databases, specific polymorphisms can be
encoded on GeneChip probe arrays and used for broad-based genotyping. The
Company intends to use these genotyping probe arrays to perform
 
                                       35
<PAGE>
genotyping services and to develop large, disease-specific databases correlating
mutations with disease. The Company intends to offer access to these databases
and genotyping probe arrays to its collaborators.
 
    As an initial step in its polymorphism discovery efforts, the Company has
entered into a consortium with Bristol-Myers and Millennium to fund research at
the Whitehead Institute to, among other research programs, identify novel
markers and study their role in disease. The Company intends to use these
markers, as well as publicly available markers and Affymetrix discovered
markers, to develop GeneChip probe arrays that can be used to map genes to their
chromosomal locations more rapidly and cost-effectively than is possible with
existing technologies. The first such GeneChip mapping array, the GeneChip Poly
2000, is currently under development. The Company intends to market these and
other mapping probe arrays to customers to facilitate genetic mapping.
 
TECHNOLOGY
 
    Affymetrix' GeneChip probe array technology and systems integrate
semiconductor fabrication techniques, solid phase chemistry, molecular biology,
software and robotics. The Company's GeneChip system consists of several
integrated components: disposable DNA probe arrays containing genetic
information on a chip housed in a cartridge, reagents for extracting and
labeling target nucleic acid, a fluidics station for introducing the test sample
to the probe arrays, a scanner to read the data from the probe arrays, and
software to control the instruments and to analyze and manage the genetic
information. The GeneChip system is designed for use by pharmaceutical and
biotechnology companies, academic research centers and clinical reference
laboratories.
 
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<PAGE>
  DNA PROBE ARRAYS
 
    The Company produces its DNA probe arrays using a process based on
semiconductor photolithographic fabrication techniques, which enables it to
assemble vast amounts of genetic information on a small glass chip called a
probe array. The genetic information is contained in sequences of DNA probes
that are built on the probe array. The Company believes that this technology
enables the efficient use of a large number of DNA probes to analyze DNA or RNA
sequences in a test sample.
 
            [Depiction of photolithographic manufacturing process.]
 
    The Company uses photolithography to synthesize a large variety of
predetermined DNA sequences simultaneously in specific locations on a glass
chip. Photolithography is a technique which uses light to create exposure
patterns on the glass chip and induce chemical reactions. The process begins by
coating the chip with light-sensitive chemical compounds that prevent chemical
coupling. The photochemically active molecules are called protecting groups.
Lithographic masks, which consist of predetermined patterns that either block or
transmit light, are used to selectively illuminate the glass surface of the
chip. Only those areas exposed to light are deprotected and thus activated for
chemical coupling through removal of the light-sensitive protecting groups. The
entire surface is then flooded with a solution containing the first in a series
of DNA building blocks (A, C, G or T). Coupling only occurs in those regions
which have been deprotected through illumination. The new DNA building block
also bears a light-sensitive protecting group so that the cycle can be repeated.
This process of exposure to light and subsequent chemical coupling can be
repeated on the same chip in order to generate an array of DNA sequences. The
intricate illumination patterns allow the Company to build high density arrays
of many diverse DNA sequences in a small area. The Company can manufacture a
large number of identical DNA probe arrays on a large glass wafer, which is then
diced into individual probe arrays.
 
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<PAGE>
    Currently, each probe array can be manufactured with thousands of
"features." Each feature can contain millions of copies of the same
single-stranded DNA sequence, or probe. The patterns of photolithographic masks
and the order of DNA building blocks used in the synthesis process dictate the
sequence of the probes in each feature on the chip surface. The number of
synthesis cycles determines the length of the DNA probes in each feature.
 
              [Depiction of GeneChip probe array and its feature.]
 
    The Company's GeneChip technology enables it to synthesize with high density
a large number of chemically diverse DNA sequences. Unlike conventional
synthesis, which generally uses a linear process to create compounds, the
Company's synthesis technology is combinatorial, in that the number of different
compounds synthesized grows exponentially with the number of cycles in the
synthesis. For example, in a 40 cycle process, Affymetrix has developed a probe
array with over one million features, each containing multiple copies of a
unique DNA sequence. This process would take over ten million cycles using
standard DNA synthesis techniques.
 
    The function of each single-stranded probe on the GeneChip probe array is to
bind to its complementary single strand of DNA or RNA from the patient sample.
Each feature on the GeneChip probe array contains identical copies of a single
strand of DNA. The nucleic acid to be tested is isolated from a sample, such as
blood or biopsy tissue, and fluorescently labeled by one of several standard
biochemical methods. The labeled test sample is then washed over the probe array
surface to bind or hybridize to the complementary probes if they are present in
the probe array. When scanned by the laser in the GeneChip scanner, the
hybridized test sample generates a fluorescent signal. The presence, sequence or
concentration of the nucleic acid sample can be determined by detecting the
relative strength of these signals since the sequence and position of each
complementary DNA probe on the probe array are known. The Company currently
manufactures probe arrays containing up to 400,000 features.
 
  INSTRUMENTATION
 
    The fluidics station controls the introduction of the test sample to the
probe array and the hybridization process. A technician places the test sample
in a small container in the fluidics station, which introduces the test sample
into the cartridge containing the DNA probe array. The technician uses a
computer to control the delivery of reagents and the timing and temperature
required for hybridization of the test sample to the probe array. The process
concludes with a reagent wash that leaves only the hybridized test sample bound
to the probe array. The fluidics station can process four probe arrays
simultaneously, typically taking less than one hour to process these arrays.
 
    After completion of hybridization on the fluidics station, the technician
places the cartridge in the scanner which reads the probe array. The GeneChip
scanner consists of a laser, high resolution optics, robotics to position and
scan the cartridge, a fluorescence detector and an interface to a personal
computer. The label on the test sample emits fluorescent signals when exposed to
the light from the laser. The intensity of the fluorescent signal is recorded by
the scanner and stored in the computer. The current scanner, which was developed
in collaboration with HP and introduced in April 1997, can read 1.28 cm by 1.28
cm probe arrays with up to 400,000 features.
 
  SOFTWARE
 
    The GeneChip product software is supplied as part of the integrated system
and runs on a Windows-TM- platform. The fluorescence intensity data captured
from the scanner are used in conjunction with computer files containing the
sequence and location of all the probes on the probe array to determine the
nucleotide sequence of the test sample. For the GeneChip HIV product, the
analysis takes less than 90 seconds for one probe array and the resulting
sequence is displayed on the computer. Customized software enables the
technician to rapidly identify polymorphisms in the test sample and to
 
                                       38
<PAGE>
compare genetic sequences across test samples. Other GeneChip software
applications enable custom probe array users to simultaneously evaluate the
relative expression levels of thousands of genes. The GeneChip software package
is compatible with most database formats.
 
CUSTOMERS, COLLABORATIVE PARTNERS AND GRANTS
 
    The Company's strategy regarding customer supply and collaborative
agreements is to establish the GeneChip system as the platform of choice for
analyzing complex genetic information, expand the applications of the Company's
technology and acquire access to complementary technologies and resources, such
as manufacturing, distribution and marketing, from its collaborative partners.
Accordingly, the Company's agreements emphasize preserving the Company's rights
to technological improvements and future business opportunities and obtaining
up-front fees or sizeable research funding commitments, as well as commitments
to purchase GeneChip systems and probe arrays. The Company's research and
development efforts have been supported in part by government grants, including
grants from the ATP and NIH. The following table sets forth a list of customers
and collaborators with whom the Company has existing agreements, the related
products and programs and the commencement dates of the agreements.
 
<TABLE>
<S>                            <C>                                    <C>              <C>
                  SUMMARY OF AFFYMETRIX CUSTOMERS AND COLLABORATORS
 
                                                                       COMMENCEMENT
    CUSTOMER/COLLABORATOR                 PRODUCT/PROGRAM                  DATE
- -----------------------------  -------------------------------------  ---------------
 
Advanced Technology Program    Miniaturized DNA analysis systems      October 1997
 
bioMerieux                     Bacteriology diagnostics               September 1996
 
Bristol-Myers, Millennium,     Functional genomics and polymorphism   April 1997
 Whitehead Institute           discovery
 
DNAX (Schering-Plough)         GeneChip expression technology         July 1997
 
Genetics Institute             GeneChip expression technology         February 1996
 
Glaxo                          HIV disease management and genomics    January 1997
 
Hewlett-Packard                Scanner supply                         February 1997
 
Hoechst                        GeneChip expression technology         April 1997
 
Incyte                         LifeChip databases                     August 1997
 
Merck                          GeneChip expression technology         September 1997
 
National Institutes of Health  Sequencing and mapping                 August 1995
 
OncorMed                       Oncology testing services              October 1996
 
Parke-Davis (Warner-Lambert)   GeneChip expression technology         October 1996
 
Pfizer                         GeneChip expression technology         July 1997
 
Pioneer Hi-Bred                GeneChip expression technology         April 1997
 
Roche                          GeneChip expression technology --      August 1997
                               EasyAccess program
 
Tularik                        GeneChip expression technology         September 1997
</TABLE>
 
  F. HOFFMANN-LA ROCHE LTD.
 
    In August 1997, the Company entered into a three-year agreement with Roche
and its affiliates for supply of standard and custom expression arrays for use
in Roche's worldwide pharmaceutical research and development activities.
Pursuant to the agreement, Roche became the Company's first EasyAccess customer,
which will allow Roche access to up to tens of thousands of probe arrays and the
opportunity
 
                                       39
<PAGE>
to create up to 100 million or more expression datapoints. Under the terms of
the agreement, Roche will pay the Company annual subscription fees for such
access to the GeneChip expression technology, per probe array fees and any
custom design fees.
 
    Prior to the 1997 agreement, the Company had entered into two agreements
with Roche in 1996. In October 1996, the Company signed a demonstration
agreement with Roche for the development and supply of a single custom probe
array containing bacterial genes. In December 1996, the Company signed a pilot
agreement with Roche Bioscience, a division of Syntex (U.S.A.) Inc., for the
development and supply of a single custom probe array containing human, rat and
mouse genes. The milestones of these agreements were met and the agreements have
been concluded.
 
  GENETICS INSTITUTE INC.
 
    In December 1995, the Company and Genetics Institute entered into a supply
agreement under which the Company agreed to manufacture and supply custom probe
arrays based on specific genes identified and selected by Genetics Institute.
Pursuant to the agreement, the Company is obligated to develop custom probe
arrays until February 1998 and to supply certain minimum quantities of the
custom probe arrays developed for Genetics Institute until February 2001. The
Company will receive fees for the design and delivery of the custom probe
arrays, as well as certain milestone payments and royalties on certain
therapeutic compounds, if discovered by Genetics Institute using these probe
arrays.
 
    Pursuant to an earlier collaboration agreement with Genetics Institute
entered into in November 1994, Genetics Institute provided research funding to
the Company for the development of DNA probe arrays to enable Genetics Institute
to discover new genes and uses for genes. The Company has completed performance
of the 1994 agreement and, accordingly, development funding under the
collaboration agreement has been discontinued. Affymetrix has agreed to supply
custom probe arrays developed under the collaboration agreement to Genetics
Institute in accordance with the supply agreement. Genetics Institute has all
rights to therapeutic compounds discovered through the use of DNA probe arrays
provided by the Company, and the Company will receive royalties and milestone
payments on certain therapeutic compounds. The Company retains rights to
enhancements to the GeneChip system technology developed in the collaboration.
The Company and Genetics Institute are negotiating amendments to their existing
agreements.
 
  OTHER SUPPLY AGREEMENTS
 
    The Company has supply agreements in genomics with several other
pharmaceutical and biotechnology companies that cover either standard or custom
probe arrays for gene expression or both. Under the terms of these agreements,
the Company will receive fees for each probe array, as well as, in some cases,
revenue from probe array design fees and instrument and software sales,
milestone payments and royalties. Current customers include DNAX Research
Institute of Molecular & Cellular Biology, Inc. (a subsidiary of Schering-Plough
Corporation) ("DNAX"), Glaxo, Hoechst, Merck, Millennium, OncorMed, Parke-Davis,
Pfizer, Pioneer Hi-Bred and Tularik, Inc.
 
  WHITEHEAD CONSORTIUM
 
    In April 1997, the Company, Bristol-Myers and Millennium entered into a
corporate consortium to fund a five-year research program in functional genomics
at the Whitehead Institute. The new program, under the direction of Dr. Eric S.
Lander, Director of the Whitehead Institute, seeks to advance the development of
gene-based technologies for research and health care.
 
    Under the terms of the consortium agreement, Affymetrix, Bristol-Myers and
Millennium will support a program of research initiated by scientists at the
Whitehead Institute to develop the next generation of genomics technologies for
the scientific community. The three companies will provide funds and
 
                                       40
<PAGE>
technology totaling approximately $8.0 million per year for five years to the
Whitehead Institute. Scientists at the companies will also collaborate with
scientists at the Whitehead Institute to identify novel genetic markers and
develop new genomics tools. In return, Affymetrix, Bristol-Myers and Millennium
will receive certain licensing rights to inventions funded by the consortium or
emerging from the use of contributed technology, subject to the payment of cross
royalties. Affymetrix has exclusive rights to commercialize consortium
inventions related to nucleic acid probe arrays and joint rights with Millennium
to commercialize diagnostic products and services and certain other products
that may arise from the consortium.
 
  BIOMERIEUX VITEK, INC.
 
    In September 1996, the Company and bioMerieux entered into a five-year
collaborative development agreement and associated supply agreement for probe
arrays to identify the species and drug resistance profiles of bacteria causing
human infection. As part of the collaboration, bioMerieux is developing
instrumentation for the use of these probe arrays in a clinical diagnostic
setting. The agreement provides that the Company will not market or provide
probe arrays for such tests to others that are in a format that would reasonably
be considered approvable by the FDA for clinical diagnostic use. Under the terms
of the agreements, bioMerieux provides research and development support and will
make payments to Affymetrix upon achievement of certain milestones. Three such
milestones have been met to date. In addition, bioMerieux will pay specified
prices for the supply of probe arrays and royalties on any resulting products.
 
  HEWLETT-PACKARD COMPANY
 
    The Company entered into a collaborative agreement with HP in November 1994,
which was amended in February 1997. Under the terms of the agreement, HP
manufactures scanners for Affymetrix. Affymetrix has all marketing rights for
its GeneChip products, including the scanners. The agreement provides for
cooperation between Affymetrix and HP for worldwide distribution and instrument
services. Pursuant to the agreement, HP is required to supply all the Company's
forecasted requirements for scanners until February 2000 and Affymetrix is
required to purchase a minimum number of scanners from HP during the same
three-year period.
 
  INCYTE PHARMACEUTICALS, INC.
 
    In November 1996, Incyte and the Company entered into a joint program to
develop and commercialize novel and disease-specific gene expression databases
and services. This agreement is an expansion of a feasibility agreement
initiated in April 1996. Under the terms of the agreement, novel and
disease-specific genes will be selected from Incyte's LifeSeq-TM- genomic
databases to generate DNA probe arrays using the GeneChip system. The resulting
LifeChip products will allow the generation of information on the preselected
genes across biological specimens to identify molecules and expression patterns
associated with human disease. Initially, probe arrays derived from LifeSeq
information will be designed for use in such fields as prostate and breast
cancer, inflammation, and G-protein coupled receptor pathways. The Company and
Incyte will share all profits and co-own the intellectual property generated
under the collaboration. The agreement may be terminated by either company upon
30 days written notice.
 
  ADVANCED TECHNOLOGY PROGRAM (UNITED STATES DEPARTMENT OF COMMERCE)
 
    In October 1994, the Company and Molecular Dynamics Inc. ("Molecular
Dynamics") were awarded a $31.5 million five-year grant to develop novel
point-of-care diagnostic systems under the ATP. Pursuant to the grant, $20.8
million is designated for the Company and its subcontractors and $10.7 million
for Molecular Dynamics and its subcontractors subject to the requirement of each
company to match such funding. The grant specifies the development of an
advanced miniaturized nucleic acid
 
                                       41
<PAGE>
diagnostic device intended to reduce the costs and increase the speed and
reliability of DNA diagnostic tests. The device would be used in point-of-care
settings, such as hospitals, clinics and doctors' offices and would require FDA
approval. The Company has successfully developed a prototype of the device and
is pursuing further development. There can be no assurance that the device will
be successfully developed or, if developed, that it will receive regulatory
approval or be successfully marketed.
 
    The research agreements between the Company and its subcontractors under the
ATP grant (the University of California, Stanford University and the University
of Washington) require that the universities assign the rights to any project
inventions made by them to the Company, subject to specified royalty payments.
The ATP agreement provides that the Company and Molecular Dynamics retain rights
in their respective fields to intellectual property developed as part of the
project.
 
    The ATP grant is administered by the United States Department of Commerce.
As of June 30, 1997, the Company had recognized $5.3 million in revenue under
the ATP grant. The grant is subject to yearly appropriations by the United
States Congress for the ATP program. There can be no assurance that funding for
the ATP program will not be reduced or eliminated at any time. The reduction or
elimination of the ATP grant could have a material adverse effect on the
Company's business, financial condition and results of operations.
 
  NATIONAL INSTITUTES OF HEALTH
 
    In August 1995, the Company was awarded a $6.0 million, three-year grant
from the NIH National Center for Human Genome Research, for a project entitled
"Sequencing and Mapping with DNA Probe Arrays." As of June 30, 1997, the Company
had recognized revenue of $2.3 million related to the grant. Under the project,
the Company is developing applications of DNA probe arrays for larger scale gene
sequencing and creating a laboratory at the Company for use by outside
researchers. The grant also includes a subcontract with Stanford University to
continue research and development of the DNA probe array technology. There can
be no assurance that the NIH will obtain the necessary funding from the United
States Congress to continue to fund this grant.
 
MANUFACTURING
 
    The Company's current strategy is to manufacture its disposable DNA probe
arrays and fluidics stations in-house and contract with third-party suppliers to
manufacture the scanner for its GeneChip system.
 
    The Company is currently manufacturing limited quantities of probe arrays
for internal and collaborative purposes and for initial research only product
sales. Currently, the Company has the capacity to produce approximately 80,000
probe arrays annually at its existing manufacturing facility located in
Sunnyvale, California. Expansion is underway to increase this facility's
capacity to more than 400,000 probe arrays annually during 1998. The Company is
also currently seeking to establish a second manufacturing site that will
further increase its manufacturing capacity and reduce operating risks. The
Company expects that this facility will be operative by the end of 1999. See
"Risk Factors--Limited Manufacturing Capability; Sole Source Suppliers."
 
    The Company's probe array manufacturing process involves wafer preparation,
probe synthesis, dicing of synthesized wafers into chips, assembly of chips into
cartridges, and quality control. Affymetrix has developed software programs that
semi-automatically design photolithographic masks used in probe array
manufacturing and control the probe array manufacturing lines. Glass wafers are
prepared for synthesis through the application of chemical coatings. DNA probes
are synthesized on the wafers using the Company's proprietary photolithographic
process. The completed wafers are then diced to yield individual probe arrays,
which are assembled into disposable cartridges and packaged for shipment. There
can be no assurance that manufacturing and quality control problems will not
arise as the
 
                                       42
<PAGE>
Company attempts to scale-up its manufacturing facilities or that such scale-up
can be achieved in a timely manner or at commercially reasonable costs.
 
    The Company relies on outside vendors to manufacture its scanners. The
Company's first generation scanner, which can read up to 64,000 features per
1.28 cm by 1.28 cm probe array was manufactured for the Company by Molecular
Dynamics. The Company's second generation scanner, developed in collaboration
with HP and introduced in April 1997, can read probe arrays with up to 400,000
features per 1.28 cm by 1.28 cm probe array.
 
                                       43
<PAGE>
    In November 1995, the Company entered into an agreement with RELA, a private
company, for the supply of fluidics stations. RELA manufactured fluidics
stations for the Company pursuant to the agreement until September 1997. In
September 1997, the Company terminated the agreement and commenced the
manufacture of fluidics stations internally.
 
    The GeneChip system is a complex set of instruments and includes DNA probe
arrays, which are produced in an innovative and complicated manufacturing
process. Due to the complexity and limited operating history of these products,
the Company anticipates that additional technical problems may occur or be
discovered as more systems are placed into operation. If these problems cannot
be readily addressed, they could cause delays in shipments, warranty expenses
and damages to customer relationships.
 
    Although the Company does not currently need to comply with GMP to
manufacture probe arrays and related instrumentation for sale for research
purposes only, it may need to be GMP compliant to sell these products to
clinical reference laboratories and it will need to be compliant to sell these
products for clinical use.
 
SALES AND MARKETING
 
    The base price of the Company's GeneChip system (scanner, software,
workstation and fluidics station) starts at approximately $135,000. The
Company's HIV probe arrays, currently being sold commercially for research use,
are priced at $45 per array, with two arrays (one for each strand of DNA)
presently used per test. The Company's p53 GeneChip assay is being sold for
research use at $100 per array. The Company is offering different access plans
to its expression technology centered around a pricing model that is based on
the number of data points and value of the collection of genes being monitored
on a particular GeneChip probe array. Actual pricing depends on several factors,
including: the magnitude of the research effort, whether the genes being
monitored are human or those of other organisms, whether intellectual property
is to be retained, shared or disclosed, whether the Company provides custom
probe array design or screening services to a customer and the amount of any
up-front fees, milestones, royalties or other payments to be received by the
Company.
 
    The Company is currently directly marketing the GeneChip system and probe
arrays for genomics and disease management applications to its customers and
collaborators. To augment these efforts the Company intends to enter into
arrangements with agents and distributors. The Company's near term strategy is
to commercialize the GeneChip system for research use only and to seek
regulatory approval for and to commercialize GeneChip probe arrays for clinical
use through partnerships with established firms in the diagnostics industry. The
Company believes that the primary market for genomics and disease management
GeneChip applications will be pharmaceutical and biotechnology companies,
academic research centers and clinical reference laboratories. As of September
30, 1997, the Company had placed 38 GeneChip systems for research use.
 
    Affymetrix has marketing and technical support groups to promote and service
its GeneChip products, which the Company intends to expand as necessary. In
addition, the Company has retained a marketing communications firm with
expertise in biotechnology to assist it in its promotional activities.
 
    The Company anticipates a long sales cycle to market the GeneChip system to
its potential customers. There can be no assurance that the Company will be able
to establish agency or distribution arrangements to market its products. See
"Risk Factors--Limited Sales and Marketing Experience."
 
RESEARCH AND DEVELOPMENT
 
    The Company believes that substantial investment in research and development
is essential to obtaining a long-term competitive position in the genomics,
disease management and polymorphism discovery fields. Affymetrix focuses on four
types of research and development: applied research,
 
                                       44
<PAGE>
primarily aimed at generating polymorphism databases; core technology
development, such as the design of fully integrated systems for complex genetic
information management; novel manufacturing methods to improve the efficiency of
the Company's probe array production processes; and basic research to explore
and expand the potential uses of DNA probe arrays and to discover new
technologies.
 
  APPLIED RESEARCH
 
    Affymetrix is focusing its applied research efforts on the development of
assays and databases to link genetic polymorphisms to human disease. The Company
believes that such databases will ultimately lead to the discovery of novel
therapeutics and the identification of diagnostic markers useful in
cost-effective disease management. The Company has established a relationship
with the Whitehead Institute at MIT to identify genetic markers that can be used
to rapidly obtain high-resolution maps of individual human genomes and thereby
identify differences among those genomes that are characteristic of particular
diseases.
 
  CORE TECHNOLOGY DEVELOPMENT
 
    The Company conducts research in several core areas, including the
development of miniaturized immobilized nucleic acid detection devices. The
intent of these development programs is to create advanced systems for complex
genetic information and products that can eventually be developed by diagnostic
partners for use in hospitals, clinical reference laboratories, and
point-of-care testing.
 
  NOVEL MANUFACTURING METHODS
 
    The Company conducts research aimed at improving the photolithographic
manufacturing process currently employed in the production of the Company's
GeneChip probe arrays. The Company is also pursuing research aimed at further
improving its manufacturing technology. In the Company's photoresistance
manufacturing research program, the Company has demonstrated an ability to
manufacture probe arrays with sub-5 micron feature sizes.
 
  BASIC RESEARCH
 
    Affymetrix' basic research efforts are focused on expanding the applications
of the GeneChip technology and developing related new technologies. These
efforts include improving the sensitivity of the GeneChip assays, increasing
information capacity per probe array and simplifying the process for conducting
highly complex assays.
 
    The Company's research and development expenses for the years ended December
31, 1994, 1995, and 1996 were $9.5 million, $12.4 million, and $18.8 million,
respectively. For the six months ended June 30, 1996 and 1997, research and
development expenses were $8.3 million and $12.7 million, respectively.
 
INTELLECTUAL PROPERTY
 
    Affymetrix has been issued 27 patents in the United States and holds over 78
pending United States patent applications. Many of these patents and
applications have been filed and/or issued in one or more foreign countries.
Affymetrix also relies upon copyright protection, trade secrets, know-how,
continuing technological innovation and licensing opportunities to develop and
maintain its competitive position. The Company's success will depend in part on
its ability to obtain patent protection for its products and processes, to
preserve its copyrights and trade secrets, to operate without infringing the
proprietary rights of third parties and to acquire licenses related to enabling
technology or products.
 
                                       45
<PAGE>
    The Company is party to various option and license agreements with third
parties (including Stanford University, Scientific Generics, Ltd., Concordia
University, OncorMed and the University of California) which give it rights to
use certain technologies. Failure of the Company to maintain rights to such
technology could have a material adverse effect on the Company's business,
financial condition and results of operations. For example, inability of the
Company to exercise the option for Stanford University technology relating to
HIV under commercially reasonable terms could have an adverse effect on the
ability of the Company to sell its HIV probe assays.
 
    The patent positions of pharmaceutical and biotechnology companies,
including the Company, are generally uncertain and involve complex legal and
factual questions. There can be no assurance that any of the Company's pending
patent applications will result in issued patents, that the Company will develop
additional proprietary technologies that are patentable, that any patents issued
to the Company or its strategic partners will provide a basis for commercially
viable products or will provide the Company with any competitive advantages or
will not be challenged by third parties, or that the patents of others will not
have an adverse effect on the ability of the Company to do business. In
addition, patent law relating to the scope of claims in the technology fields in
which the Company operates is still evolving. The degree of future protection
for the Company's proprietary rights, therefore, is uncertain. Furthermore,
there can be no assurance that others will not independently develop similar or
alternative technologies, duplicate any of the Company's technologies, or, if
patents are issued to the Company, design around the patented technologies
developed by the Company. In addition, the Company could incur substantial costs
in litigation to defend itself in patent suits brought by third parties, or if
it initiates such suits.
 
    The commercial success of the Company also depends in part on the Company
neither infringing patents or proprietary rights of third parties nor breaching
any licenses that may relate to the Company's technologies and products. For
example, the Company, its collaborators and customers may need to acquire a
license for an amplification technology to use the GeneChip system in certain
applications, and there is no assurance such a license will be available on
commercially reasonable terms. Furthermore, the Company is aware of third-party
patents that may relate to the Company's technology, including reagents used in
probe array synthesis and in probe array assays, probe array scanners, synthesis
techniques, oligonucleotide amplification techniques, assays, and probe arrays.
There can be no assurance that the Company will not infringe on these patents or
other patents or proprietary rights of third parties or that the Company would
be able to obtain a license to such patents or proprietary rights on
commercially acceptable terms, if at all. In addition, the Company has received
and may in the future receive a notice claiming infringement from third parties
as well as invitations to take licenses under third party patents.
 
    The Company is aware of patents and patent applications owned by Isis
Innovation Ltd. (E.M. Southern) that may relate to the Company's technology. The
Company has opposed two such allowed European patents. One such patent has also
been issued in the United States, and the Company is aware that others are
pending and may issue. One of the allowed European applications has broad claims
to certain array related technology, which claims have been opposed by the
Company. If a United States patent relating to arrays issues with claims as
broad as the European patent, the Company could be subject to infringement
claims that could delay or preclude sales of some or all of its products, which
would have a material adverse effect on the Company's business, financial
condition and results of operations. If the Company were required to obtain a
license to any such patent, there can be no assurance that such license could be
acquired on commercially acceptable terms, if at all.
 
    On March 3, 1997, Hyseq filed a lawsuit in United States District Court for
the Northern District of California (San Jose Division) alleging that certain
Affymetrix products infringe United States patents 5,202,231 and 5,525,464. The
Hyseq action and any other legal action against the Company or its collaborative
partners claiming damages and seeking to enjoin commercial activities relating
to the affected products and processes could, in addition to subjecting the
Company to potential liability for
 
                                       46
<PAGE>
damages, require the Company or its collaborative partners to obtain a license
in order to continue to manufacture or market the affected products and
processes. While the Company believes that the Hyseq complaint is without merit,
there can be no assurance that the Company will prevail in the Hyseq action or
that the Company or its collaborative partners will prevail in any other action,
nor can there be any assurance that any license (including licenses proposed by
third parties) required would be made available on commercially acceptable
terms, if at all.
 
    There are a significant number of United States and foreign patents and
patent applications in the Company's areas of interest, and the Company believes
that there may be significant litigation in the industry regarding patent and
other intellectual property rights. The Hyseq action and any other such
litigation could consume substantial managerial and financial resources, which
could have a material adverse effect on the Company's business, financial
condition and results of operations. Further, because of the substantial amount
of discovery required in connection with any such litigation, there is a risk
that confidential information could be compromised by disclosure.
 
    Others may have filed and in the future are likely to file patent
applications that are similar or identical to those of the Company or those of
its licensors. To determine the priority of inventions, the Company may have to
participate in interference proceedings declared by the United States Patent and
Trademark Office that could result in substantial cost to the Company. No
assurance can be given that any such patent application will not have priority
over patent applications filed by the Company.
 
    The enactment of legislation implementing the General Agreement on Trade and
Tariffs has resulted in certain changes in United States patent laws that became
effective on June 8, 1995. Most notably, the term of patent protection for
patent applications filed on or after June 8, 1995 is no longer a period of
seventeen years from the date of grant. The new term of United States patents
will commence on the date of issuance and terminate twenty years after the
earliest effective filing date of the application. Because the time from filing
to issuance of biotechnology patent applications in the Company's area of
interest is often more than three years, a twenty-year term after the effective
date of filing may result in a substantially shortened term of the Company's
patent protection, which may adversely affect the Company's patent position.
 
    The Company also relies upon copyright and trade secret protection for its
confidential and proprietary information. There can be no assurance, however,
that such measures will provide adequate protection for the Company's trade
secrets or other proprietary information. In addition, there can be no assurance
that proprietary information will not be disclosed, that others will not
independently develop substantially equivalent proprietary information and
techniques or otherwise gain access to the Company's copyrights and trade
secrets or disclose such technology, or that the Company can effectively protect
its trade secrets.
 
    The Company's academic collaborators have certain rights to publish data and
information in which the Company has rights. There is considerable pressure on
academic institutions to publish discoveries in the genetics and genomics
fields. There can be no assurance that such publication would not adversely
affect the Company's ability to obtain patent protection for some genes in which
it may have a commercial interest.
 
GOVERNMENT REGULATION
 
    The manufacturing, labeling, distribution and marketing of some or all of
the Company's disease management products are subject to government regulation
in the United States and in certain other countries.
 
    In the United States, the FDA regulates, as medical devices, most diagnostic
tests and IN VITRO reagents that are marketed as finished test kits or
equipment. Some clinical laboratories, however, purchase individual reagents
intended for specific analyses, and use those reagents to develop and
 
                                       47
<PAGE>
prepare their own finished diagnostic tests. Although the FDA has not generally
exercised regulatory authority over these individual reagents or the finished
tests prepared from them by the clinical laboratories, the FDA has proposed a
rule that, if adopted, would regulate reagents sold to clinical laboratories as
medical devices. The proposed rule would also restrict sales of these reagents
to clinical laboratories certified under CLIA as high complexity laboratories.
The Company intends to market some diagnostic products as finished test kits or
equipment and others as individual reagents; consequently, some or all of these
products may be regulated as medical devices.
 
    The Food, Drug, and Cosmetic Act requires that medical devices introduced to
the United States market, unless exempted by regulation, be the subject of
either a premarket notification clearance (known as a "510(k)") or PMA. Some of
the Company's products and those of its collaborators may require a PMA and
others may require a 510(k). With respect to devices reviewed through the 510(k)
process, a company may not market a device until an order is issued by the FDA
finding the product to be substantially equivalent to a legally marketed device
known as a "predicate device." A 510(k) submission may involve the presentation
of a substantial volume of data, including clinical data, and may require a
substantial review. The FDA may agree that the product is substantially
equivalent to a predicate device and allow the product to be marketed in the
United States. The FDA, however, may (i) determine that the device is not
substantially equivalent and require a PMA, or (ii) require further information,
such as additional test data, including data from clinical studies, before it is
able to make a determination regarding substantial equivalence. By requesting
additional information, the FDA can further delay market introduction of a
company's products. If the FDA indicates that a PMA is required for any of the
Company's products, the application will require extensive clinical studies,
manufacturing information (including demonstration of compliance with GMP
requirements) and likely review by a panel of experts outside the FDA. Clinical
studies to support either a 510(k) submission or a PMA application would need to
be conducted in accordance with FDA requirements. Failure to comply with FDA
requirements could result in the FDA's refusal to accept the data or the
imposition of regulatory sanctions. FDA review of a PMA application could take
significantly longer than that for a 510(k).
 
    There can be no assurance that the Company or its collaborators will be able
to meet the FDA's requirements or that any necessary approval will be received.
Once granted, a 510(k) clearance or PMA approval may place substantial
restrictions on how the device is marketed or to whom it may be sold. Even where
a device is exempted from 510(k) clearance or PMA approval, the FDA may impose
restrictions on its marketing. In addition to requiring clearance or approval
for new products, the FDA may require clearance or approval prior to marketing
products that are modifications of existing products. There can be no assurance
that any necessary 510(k) clearance or PMA approval will be granted on a timely
basis or at all. FDA imposed restrictions could limit the number of customers to
whom particular products could be marketed or what may be communicated about
particular products. Delays in receipt of or failure to receive any necessary
510(k) clearance or PMA, or the imposition of stringent restrictions on the
Company's labeling and sales of its products could have a material adverse
effect on the Company.
 
    As a medical device manufacturer, the Company would also be required to
register and list its products with the FDA. In addition, the Company would be
required to comply with the FDA's GMP regulations, which require that medical
devices be manufactured and records be maintained in a prescribed manner with
respect to manufacturing, testing and control activities. Further, the Company
would be required to comply with FDA requirements for labeling and promotion of
its medical devices. For example, the FDA prohibits cleared or approved devices
from being marketed for uncleared or unapproved uses. In addition, the medical
device reporting regulation would require that the Company provide information
to the FDA whenever there is evidence to reasonably suggest that one of its
devices may have caused or contributed to a death or serious injury, or that
there has occurred a malfunction that would be likely to cause or contribute to
a death or serious injury if the malfunction were to recur.
 
                                       48
<PAGE>
    Medical device manufacturers are subject to periodic inspections by the FDA
and state agencies. Additionally, the FDA will conduct a preapproval inspection
for all PMA devices and in some cases for 510(k) devices as well. If the FDA
believes that a company is not in compliance with applicable laws or
regulations, it can institute proceedings to issue a warning or other letter
apprising of violative conduct, detain or seize products, issue a recall, enjoin
future violations and assess civil and criminal penalties against the company,
its officers or its employees. In addition, clearances or approvals could be
suspended or withdrawn in appropriate circumstances. Failure to comply with
regulatory requirements or any adverse regulatory action could have a material
adverse effect on the Company.
 
    Medical device laws and regulations are also in effect in many of the
countries in which the Company may do business outside the United States. These
range from comprehensive device approval requirements for some or all of the
Company's medical device products to requests for product data or
certifications. The number and scope of these requirements are increasing. There
can be no assurance that the Company will obtain regulatory approvals in such
countries or that it will not be required to incur significant costs in
obtaining or maintaining its foreign regulatory approvals. In addition, the
export by the Company of certain of its products which have not yet been cleared
for domestic commercial distribution may be subject to FDA export restrictions.
The failure to obtain product approvals in a timely fashion or to comply with
state or foreign medical device laws and regulations may have a material adverse
impact on the Company. Medical device laws and regulations are also in effect in
some states in which the Company does business.
 
    In addition, federal, state and foreign laws and regulations regarding the
manufacture and sale of medical devices are subject to future changes. For
example, the FDA has recently made significant changes in its regulations
regarding medical device GMPs and it is considering changes to other
regulations. The Company cannot predict what impact, if any, such changes might
have on its business; however, such changes could have a material impact on the
Company.
 
    Any of the Company's customers using its diagnostic devices for clinical use
in the United States may be regulated under CLIA. CLIA is intended to ensure the
quality and reliability of clinical laboratories in the United States by
mandating specific standards in the areas of personnel qualifications,
administration, participation in proficiency testing, patient test management,
quality control, quality assurance and inspections. The regulations promulgated
under CLIA establish three levels of diagnostic tests ("waived," "moderately
complex" and "highly complex") and the standards applicable to a clinical
laboratory depend on the level of the tests it performs. CLIA requirements may
prevent some clinical laboratories from using certain of the Company's
diagnostic products. In addition, the FDA has proposed regulation of certain
"analyte specific reagents" used in clinical reference laboratories. There can
be no assurance that the CLIA regulations and future administrative
interpretations of CLIA or future regulatory requirements of the FDA will not
have a material adverse impact on the Company by imposing new regulatory
requirements or by limiting the potential market for the Company's products.
 
    The Company is also subject to numerous environmental and safety laws and
regulations, including those governing the use storage and disposal of hazardous
and biological materials. Any violation of, and the cost of compliance with,
these regulations could have a material adverse effect on the Company's
business, financial condition and results of operations.
 
REIMBURSEMENT
 
    The ability of the Company, its collaborators and other pharmaceutical and
biotechnology companies to successfully commercialize their products may depend
on their ability to obtain adequate levels of reimbursement for certain health
care products and services in the United States, Europe and other countries. The
availability of third-party reimbursement for such products and services may be
limited or uncertain, particularly with respect to genetic tests and other
disease management products.
 
    In the United States, the cost of medical care is funded, in substantial
part, by government insurance programs, such as Medicare and Medicaid, and
private and corporate health insurance plans. Third-
 
                                       49
<PAGE>
party payors may deny reimbursement if they determine that a prescribed health
care product or service has not received appropriate FDA or other governmental
regulatory clearances, is not used in accordance with cost-effective treatment
methods as determined by the payor, or is experimental, unnecessary or
inappropriate. The ability of the Company, its collaborators and other
pharmaceutical and biotechnology companies to commercialize certain of their
products and services successfully may depend on the extent to which appropriate
reimbursement levels for the costs of such products and services are obtained
from government authorities, private health insurers and other organizations,
such as HMOs. Third-party payors are increasingly challenging the prices charged
for health care products and services. The trend towards managed health care in
the United States and the concurrent growth of organizations such as HMOs, which
could control or significantly influence the purchase of health care products
and services, as well as legislative proposals to reform health care or reduce
government insurance programs, may all result in lower prices for health care
products and services commercialized by customers and collaborative partners of
the Company. This could reduce the amount of future royalty payments that may be
due to the Company on such product sales or services. The cost containment
measures that health care providers are instituting and the impact of any health
care reform may also adversely affect the profits of the Company's customers and
collaborative partners. As a result, pharmaceutical and biotechnology companies
may choose to reduce or eliminate certain research and development programs that
utilize the Company's products. A reduction of royalty payments to the Company
or the reduction or cancellation of research programs that utilize the Company's
products could have a material adverse effect on the Company's business,
financial condition and results of operations.
 
COMPETITION
 
    Competition in genomics, disease management and polymorphism discovery is
intense and expected to increase. Further, the technologies for discovering
genes and polymorphisms associated with significant diseases and approaches for
commercializing those discoveries are new and rapidly evolving.
 
    Currently, the Company's principal competition comes from existing
technologies that are used to perform many of the same functions for which the
Company plans to market its GeneChip systems. In the diagnostic field, these
technologies are provided by established diagnostic companies such as Abbott
Laboratories, Roche Boehringer Mannheim, Johnson & Johnson and SmithKline
Beecham plc. These technologies include a variety of established assays, such as
immunoassays, histochemistry, flow cytometry and culture, and newer DNA probe
diagnostics to analyze certain limited amounts of genetic information.
 
    In the genomics and polymorphism discovery fields, existing competitive
technologies include gel-based sequencing using instruments provided by
companies such as the Applied Biosystems division of Perkin-Elmer and Amersham
Pharmacia Biotech Ltd. In order to compete against existing technologies, the
Company will need to demonstrate to potential customers that the GeneChip system
provides improved performance and capabilities. Future competition in these
fields will likely come from existing competitors as well as other companies
seeking to develop new technologies for sequencing and analyzing genetic
information. In addition, pharmaceutical and biotechnology companies, such as
Genome Therapeutics, Genset, HGS, Incyte, Millennium, Myriad and Sequana have
significant needs for genomic information and may choose to develop or acquire
competing technologies to meet these needs. Other companies such as Digital Gene
Technologies, CuraGen, Gene Logic, Hyseq, Nanogen, Synteni and Visible Genetics
also are developing or have developed DNA probe based assays or other products
and services, some of which may be competitive with those of the Company.
 
    The market for disease management products derived from gene discovery is
currently limited and will be highly competitive. Many companies are developing
and marketing DNA probe tests for genetic and other diseases. Other companies
are conducting research on new technologies for diagnostic tests based on
advances in genetic information. Established diagnostic companies could provide
significant
 
                                       50
<PAGE>
competition to Affymetrix through the development of new products. These
companies have the strategic commitment to diagnostics, the financial and other
resources to invest in new technologies, substantial intellectual property
portfolios, substantial experience in new product development regulatory
expertise, manufacturing capabilities and the distribution channels to deliver
products to customers. These companies also have an installed base of
instruments in several markets, including clinical and reference laboratories,
which are not compatible with the GeneChip system. In addition, these companies
have formed alliances with genomics companies which provide them access to
genetic information that may be incorporated into their diagnostic tests.
 
EMPLOYEES
 
    As of September 30, 1997, Affymetrix had 217 full-time employees, 46 of whom
hold Ph.D. or M.D. degrees. The employee group includes chemists, engineers,
computer scientists, mathematicians and molecular biologists with experience in
the diagnostic products, medical products, semiconductor, computer software and
electronics industries. None of the Company's employees is represented by a
collective bargaining agreement, nor has the Company experienced work stoppages.
The Company believes that it maintains good relationships with its employees.
Affymetrix' success will depend in large part on its ability to attract and
retain skilled and experienced employees. There can be no assurance that the
Company will be successful in hiring or retaining qualified personnel, and its
failure to do so could have a material adverse impact on the Company's business,
financial condition and results of operations.
 
FACILITIES
 
    Affymetrix leases two facilities in Santa Clara, California totaling 101,000
square feet for research laboratories and administrative offices under a lease
expiring in 2003. The Company has an option to renew the leases on these
facilities for an additional three years. The Company leases 20,000 square feet
of space for manufacturing operations in Sunnyvale, California under a lease
that expires in 2000. The Company has options to renew this lease for two
successive three-year terms. The Company also leases 31,000 square feet of
research and development space in Sunnyvale, California under a lease that
expires in 1999. The Company expects to add a second manufacturing facility by
the end of 1999, as well as to expand its existing research and development
facilities over the next few years.
 
SCIENTIFIC ADVISORY BOARD
 
    The members of the Company's Scientific Advisory Board have made significant
contributions to the development of the Company's technologies. Each scientific
advisor spends between one day per week and one day per quarter working on
Company projects.
 
    The members of the Affymetrix Scientific Advisory Board are as follows:
 
    PAUL BERG, PH.D., is Cahill Professor in Cancer Research, Professor of
Biochemistry and Director of the Beckman Center for Molecular and Genetic
Medicine at Stanford University School of Medicine. He received the Nobel Prize
in Chemistry in 1980, the National Medal of Science in 1983 and is a member of
the National Academy of Sciences, the Royal Society, London, and the French
Academy of Sciences. Dr. Berg also serves as a member of the Company's Board of
Directors.
 
    MARK M. DAVIS, PH.D., is a Professor of Microbiology and Immunology at
Stanford University and an investigator of the Howard Hughes Medical Institute.
He received his Ph.D. from the California Institute of Technology in molecular
biology and was a postdoctoral and staff fellow at the NIH. He is well-known for
his work on antigen recognition by the immune system and has received numerous
awards, including a General Motors prize for work of importance to cancer
biology as well as awards from the Gardner Foundation and the King Faisal
Foundation. He is a member of the National Academy of Sciences.
 
    RONALD W. DAVIS, PH.D., is Professor of Biochemistry and Genetics at
Stanford University Medical School. He was elected to the National Academy of
Sciences in 1983 and has received numerous
 
                                       51
<PAGE>
awards for his contributions to the field of genetics. He has published more
than 155 papers. Dr. Davis' research focuses on developing new technologies and
instrumentation to study genomic organization and whole genome analysis,
including whole genome DNA sequencing, gene expression, gene deletion,
functional analysis, protein interaction, drug targeting, point mutational
analysis and allelic variation in the human genome.
 
    ERIC LANDER, D. PHIL., is the Director of the Whitehead Institute/MIT Center
for Genome Research and Professor of Biology at the Massachusetts Institute of
Technology. Dr. Lander was a MacArthur Prize Fellow from 1987 to 1992 and is a
member of the National Academy of Sciences. Dr. Lander's research focuses on
genetic mapping and genome structure in the mouse and human, genetic analysis of
polygenic traits and population genetics of human diseases.
 
    JOSHUA LEDERBERG, PH.D., is Sackler Foundation Scholar and Research
Geneticist at Rockefeller University, where he was President from 1978 to 1990.
Dr. Lederberg received the Nobel Prize in Medicine in 1958 for his research in
the genetic structure and function of microorganisms and in 1989 was awarded the
National Medal of Science. Dr. Lederberg has been a lead investigator in
artificial intelligence programs at Stanford University and has served on the
Advisory Council on Health Research of the World Health Organization for many
years.
 
    RICHARD A. MATHIES, PH.D., is Professor of Chemistry at the University of
California, Berkeley. Dr. Mathies is an expert on the development of new methods
for the detection and analysis of biomolecules, such as capillary array
electrophoresis and photolithographic chemical analysis systems. Dr. Mathies is
assisting Affymetrix with high sensitivity fluorescence detection methodologies,
photophysics and the development of microchemical nucleic acid preparation and
analysis systems. Dr. Mathies received an NIH Merit Award in 1991 and the
American Society for Photobiology Research Award in 1989. He has received
fellowships from the Helen Hay Whitney and Alfred P. Sloan Foundations. Dr.
Mathies is a member of the National Human Genome Research Institute Advisory
Council.
 
    R. FABIAN PEASE, PH.D., is Professor of Electrical Engineering at Stanford
University. Dr. Pease's current research focuses on micro- and nano-lithography,
novel ultra-small electron devices, and advanced packaging concepts. From 1971
to 1978, he was supervisor of the electron beam exposure group at Bell
Laboratories, where he and his colleagues developed the electron beam
mask-making process that was the semiconductor industry standard for over a
decade. Dr. Pease is a member of the National Academy of Engineering. He is
assisting Affymetrix with the application of very large scale integrated circuit
technology to the development of the Company's light-directed synthesis
technology.
 
    CALVIN F. QUATE, PH.D., is Professor of Applied Physics and Electrical
Engineering at Stanford University. Dr. Quate served as senior Research Fellow
of the Xerox Palo Alto Research Center from 1984 to 1994. Dr. Quate's awards
include the IEEE Morris N. Liebmann Award (1981), Rank Prize for Opto-
Electronics (1982), IEEE Achievement Award, Ultraoxics, Ferroelectrics and
Frequency Control Society (1986), IEEE Medal of Honor (1988), President's
National Medal of Science (1992) and Foreign Member Royal Society (1995). He is
a member of the National Academy of Sciences, National Academy of Engineering
and the Royal Society (London).
 
    LUBERT STRYER, M.D., Chairman of the Scientific Advisory Board, is Winzer
Professor in the School of Medicine and Professor of Neurobiology at Stanford
University. He served as President and Scientific Director of Affymax Research
Institute and Managing Director of Affymax in 1989 and 1990. He is a co-inventor
of the Company's light-directed synthesis technology. Dr. Stryer has pioneered
the development of novel fluorescence detection techniques and holds ten patents
involving fluorescence and light-activated chemical synthesis. Dr. Stryer is the
author of BIOCHEMISTRY, a major text used widely in colleges and universities
around the world. Dr. Stryer received the American Chemical Society Award in
Biological Chemistry (the Eli Lilly Award) and is a member of the National
Academy of Sciences and received an honorary Doctor of Science from the
University of Chicago. Dr. Stryer also serves as a member of the Company's Board
of Directors and is a director of Aurora Biosciences.
 
                                       52
<PAGE>
                                   MANAGEMENT
 
EXECUTIVE OFFICERS AND DIRECTORS
 
    The executive officers and directors of the Company, and their ages as of
September 30, 1997, are as follows:
 
<TABLE>
<CAPTION>
NAME                                    AGE                                POSITION
- ----------------------------------      ---      -------------------------------------------------------------
<S>                                 <C>          <C>
Stephen P.A. Fodor................  44........   President and Chief Executive Officer and Director
Thomas R. Gingeras................  50........   Vice President, Biological Research
Karen H. Haynes...................  36........   Vice President, Human Resources and Administration
Edward M. Hurwitz.................  33........   Vice President, Chief Financial Officer
Paul M. Kaplan....................  51........   Vice President, Product Development
Robert J. Lipshutz................  42........   Vice President, Corporate Development
Vernon A. Norviel.................  38........   Vice President, General Counsel
Kenneth J. Nussbacher.............  44........   Executive Vice President
Richard P. Rava...................  40........   Senior Vice President, Operations and Technology
John D. Diekman...................  54........   Chairman of the Board
Paul Berg (1).....................  70........   Director
Douglas M. Hurt (2)...............  40........   Director
Vernon R. Loucks, Jr..............  62........   Director
Barry C. Ross.....................  49........   Director
David B. Singer (2)...............  35........   Director
Lubert Stryer.....................  59........   Director
John A. Young (1)(2)..............  65........   Director
Alejandro C. Zaffaroni (1)........  74........   Director
</TABLE>
 
- --------------
 
(1) Member of the Compensation Committee
 
(2) Member of the Audit Committee
 
    STEPHEN P.A. FODOR, PH.D., is the President and Chief Executive Officer of
the Company and has been a Director of the Company since February 1993. From
July 1995 to March 1997, Dr. Fodor served as President and Chief Operating
Officer, from September 1994 to July 1995, as President and Chief Technical
Officer and, from February 1993 until September 1994, as Chief Technical Officer
of the Company. Dr. Fodor previously was Vice President and Director of Physical
Sciences at the Affymax Research Institute from November 1992 to February 1993.
 
    THOMAS R. GINGERAS, PH.D., has served as Vice President, Biological Research
since January 1997. Dr. Gingeras joined the Company in December 1993 as Director
of Molecular Biology. From 1990 to 1993, Dr. Gingeras was Director of Baxter
Healthcare's Life Sciences Research Laboratory.
 
    KAREN H. HAYNES was appointed Vice President, Human Resources and
Administration in March 1997. From 1993 to 1997, Ms. Haynes held various human
resources management positions at Affymax and Affymetrix, most recently as
Director of Human Resources for Affymetrix from 1995 to 1997. From 1990 to 1993,
Ms. Haynes was at Lattice Semiconductor in a senior human resources position.
 
    EDWARD M. HURWITZ, J.D., joined Affymetrix in May 1997 as Vice President,
Chief Financial Officer. From April 1994 to March 1997 Mr. Hurwitz served as
Senior Biotechnology Analyst at Robertson Stephens & Company. From 1992 to 1994,
Mr. Hurwitz held the position of Senior Biotechnology Analyst at Smith Barney
Shearson.
 
    PAUL M. KAPLAN, PH.D., has been Vice President, Product Development since
joining the Company in April 1994. From 1988 to 1994, Dr. Kaplan served as Vice
President, Research and Development of the
 
                                       53
<PAGE>
Diagnostic Division at Centocor, Inc., where he was responsible for the
identification, development and commercialization of a variety of proprietary
immunoassay products.
 
    ROBERT J. LIPSHUTZ, PH.D., was appointed Vice President, Corporate
Development in March 1997. From May 1993 to February 1997 Dr. Lipshutz was
Director, Advanced Technology and Bioinformatics. From 1991 to 1993, Dr.
Lipshutz held the position of Vice President at Daniel H. Wagner, Associates.
 
    VERNON A. NORVIEL, J.D., was appointed Vice President and General Counsel of
the Company in February 1996. From 1989 to 1996, Mr. Norviel was an associate
and then a partner with Townsend and Townsend and Crew LLP.
 
    KENNETH J. NUSSBACHER, J.D., has been Executive Vice President since joining
the Company in September 1995. From September 1995 until May 1997, Mr.
Nussbacher also served as Chief Financial Officer. From 1989 to 1995, Mr.
Nussbacher held various management positions at Affymax, most recently as
Executive Vice President for Business and Legal Affairs and Managing Director of
Affymax Technologies N.V.
 
    RICHARD P. RAVA, PH.D., has served as Senior Vice President, Operations and
Technology since September 1996. From September 1994 to September 1996, Dr. Rava
was Vice President of Research and Engineering. Dr. Rava joined the Company in
February 1993 as Director of Biomedical Engineering. From 1992 to 1993, Dr. Rava
was a Senior Scientist at Affymax Research Institute.
 
    JOHN D. DIEKMAN, PH.D., has served as a Director of the Company and Chairman
since the Company's inception. Dr. Diekman served as Chief Executive Officer of
the Company from July 1995 to March 1997. Prior to that, Dr. Diekman served as
President and Chief Operating Officer of Affymax from July 1991 to March 1995
and as Chairman of the Affymax Board of Directors from July 1994 to July 1995.
Dr. Diekman also currently serves as a director of Quidel Corp. and is a partner
of Bay City Capital LLC, a life sciences merchant bank.
 
    PAUL BERG, PH.D., has been a Director of the Company since August 1993. Dr.
Berg is Cahill Professor in Cancer Research, Professor of Biochemistry and
Director of the Beckman Center for Molecular and Genetic Medicine at Stanford
University School of Medicine. He received the Nobel Prize in Chemistry in 1980,
the National Medal of Science in 1983 and is a member of the National Academy of
Sciences, the Royal Society, London, and the French Academy of Sciences. Dr.
Berg also serves as a member of the Company's Scientific Advisory Board.
 
    DOUGLAS M. HURT, a Director of the Company since June 1995, is Senior Vice
President and Chief Financial Officer of Glaxo Wellcome, Inc. Mr. Hurt has held
various financial management positions at Glaxo since 1983 and was designated by
Glaxo to serve on the Board of Directors.
 
    VERNON R. LOUCKS, JR., has been a Director of the Company since August 1993.
Mr. Loucks has served as Chief Executive Officer of Baxter International Inc.
("Baxter") since 1980 and Chairman of Baxter since 1987. Mr. Loucks also serves
as a director of The Dun and Bradstreet Corp., Emerson Electric Co., Quaker Oats
Co. and Anheuser-Busch Companies, Inc.
 
    BARRY C. ROSS, PH.D., a Director of the Company since March 1995, has served
as Director of Group Research Strategy and Alliances at Glaxo Wellcome Research
and Development Ltd. since 1995. Dr. Ross joined Glaxo in 1984 and served as
Director, Medicinal Chemistry from 1989 to 1993 and was designated by Glaxo to
serve on the Board of Directors.
 
    DAVID B. SINGER, a Director of the Company since February 1993, served as
Vice Chairman from July 1995 to April 1996. From February 1993 to June 1995, Mr.
Singer was President and Chief Executive Officer of the Company. He served as
Vice President of Finance and Treasurer of Affymax from 1991 to 1993 and as
Director of Corporate Development at Affymax from 1990 to 1991. Mr. Singer has
been Senior Vice President and Chief Financial Officer of Heartport Inc. since
May 1996.
 
                                       54
<PAGE>
    LUBERT STRYER, M.D., served as a Director of the Company since September
1996. Dr. Stryer is Winzer Professor in the School of Medicine, Stanford
University and has been a Professor of Neurobiology at Stanford University since
1976. Dr. Stryer received the American Chemical Society Award in Biological
Chemistry (Eli Lilly Award) and is a member of the National Academy of Sciences
and received an honorary Doctor of Science from the University of Chicago. Dr.
Stryer also serves as Chairman of the Company's Scientific Advisory Board.
 
    JOHN A. YOUNG has served as a Director of the Company since August 1993. Mr.
Young retired as President and Chief Executive Officer of Hewlett-Packard Co. in
October 1992. Mr. Young also serves as a director of Wells Fargo & Company,
Chevron Corp., SmithKline Beecham Corp., Novell, Inc., Lucent Technologies and
Shaman Pharmaceuticals, Inc. and is a member of the Business Council.
 
    ALEJANDRO C. ZAFFARONI, PH.D., a founder of the Company, has served as a
Director since February 1993. Dr. Zaffaroni is also the founder of Syntex
Laboratories, ALZA Corporation ("ALZA"), DNAX and Affymax. Dr. Zaffaroni served
as Chairman of Affymax from its inception to July 1994 and as Chief Executive
Officer and Managing Director of Affymax from its inception until its
acquisition by Glaxo Wellcome in March 1995. He served as Chairman and Chief
Executive Officer of ALZA from 1968 to 1987 and has been Co-Chairman of ALZA
since 1987. Dr. Zaffaroni has been Chief Executive Officer of Symyx, Inc. and
Maxygen, Inc. since their founding.
 
                                       55
<PAGE>
                            VALIDITY OF COMMON STOCK
 
    The legality of the issuance of the Common Stock offered hereby is being
passed upon for the Company by Heller Ehrman White & McAuliffe, Palo Alto,
California. The validity of the Common Stock offered hereby will be passed upon
for the Underwriters by Sullivan & Cromwell, Los Angeles, California. As of the
date of this Prospectus, Julian N. Stern, a member of Heller Ehrman White &
McAuliffe, beneficially owns 26,980 shares of the Company's Common Stock.
 
                                    EXPERTS
 
    The audited financial statements and schedules of the Company at December
31, 1995 and 1996 and for each of the three years in the period ended December
31, 1996 appearing in the prospectus and registration statement have been
audited by Ernst & Young LLP, independent auditors, as set forth in their report
thereon appearing elsewhere herein and are included in reliance upon such
report, given upon the authority of such firm as experts in accounting and
auditing.
 
    The statements in this Prospectus as set forth under the captions "Risk
Factors--Dependence on Proprietary Technology and Unpredictability of Patent
Protection" and "Business--Intellectual Property" have been passed upon by
Townsend and Townsend and Crew LLP, Palo Alto, California, patent counsel to the
Company, as experts on such matters, and are included herein in reliance upon
that review and approval.
 
                                       56
<PAGE>
                                AFFYMETRIX, INC.
                         INDEX TO FINANCIAL STATEMENTS
 
<TABLE>
<CAPTION>
                                                                                                                PAGE
                                                                                                                -----
<S>                                                                                                          <C>
Report of Ernst & Young LLP, Independent Auditors..........................................................         F-2
 
Balance Sheets.............................................................................................         F-3
 
Statements Of Operations...................................................................................         F-4
 
Statements Of Shareholders' Equity.........................................................................         F-5
 
Statements Of Cash Flows...................................................................................         F-6
 
Notes To Financial Statements..............................................................................         F-7
</TABLE>
 
                                      F-1
<PAGE>
               REPORT OF ERNST & YOUNG, LLP, INDEPENDENT AUDITORS
 
To the Board of Directors and Shareholders
Affymetrix, Inc.
 
    We have audited the accompanying balance sheets of Affymetrix, Inc. at
December 31, 1996 and 1995, and the related statements of operations,
shareholder's equity, and cash flows for each of the three years in the period
ended December 31, 1996. These financial statements are the responsibility of
the Company's management. Our responsibility is to express an opinion on these
financial statements based on our audits.
 
    We conducted our audits in accordance with generally accepted auditing
standards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements. An audit also includes
assessing the accounting principles used and significant estimates made by
management, as well as evaluating the overall financial statement presentation.
We believe that our audits provide a reasonable basis for our opinion.
 
    In our opinion, the financial statements referred to above present fairly,
in all material respects, the financial position of Affymetrix, Inc. as of
December 31, 1996 and 1995, and the results of its operations and its cash flows
for each of the three years in the period ended December 31, 1996, in conformity
with generally accepted accounting principles.
 
                                                               Ernst & Young LLP
 
Palo Alto, California
 
January 23, 1997
 
                                      F-2
<PAGE>
                                AFFYMETRIX, INC.
                                 BALANCE SHEETS
                      (IN THOUSANDS, EXCEPT SHARE AMOUNTS)
 
<TABLE>
<CAPTION>
                                                                                 DECEMBER 31,
                                                                            -----------------------
                                                                               1995        1996
                                                                            ----------  -----------    JUNE 30,
                                                                                                     ------------
                                                                                                         1997
                                                                                                     ------------
                                                                                                     (UNAUDITED)
<S>                                                                         <C>         <C>          <C>
                                                     ASSETS
Current assets:
  Cash and cash equivalents...............................................  $    2,481  $    14,143   $   34,594
  Short-term investments..................................................      36,402       94,839       60,051
  Accounts receivable.....................................................       1,342        1,888        4,480
  Inventories.............................................................         670        1,901        2,038
  Other current assets....................................................         260          523          393
                                                                            ----------  -----------  ------------
    Total current assets..................................................      41,155      113,294      101,556
 
Property and equipment
    Equipment and furniture...............................................       4,254        7,307       11,697
    Leasehold improvements................................................         586          946          999
                                                                            ----------  -----------  ------------
                                                                                 4,840        8,253       12,696
    Less accumulated depreciation and amortization........................      (1,583)      (2,856)      (3,737)
                                                                            ----------  -----------  ------------
  Net property and equipment..............................................       3,257        5,397        8,959
 
Other assets..............................................................         140          169          985
                                                                            ----------  -----------  ------------
                                                                            $   44,552  $   118,860   $  111,500
                                                                            ----------  -----------  ------------
                                                                            ----------  -----------  ------------
 
                                      LIABILITIES AND SHAREHOLDERS' EQUITY
Current liabilities:
  Accounts payable and accrued liabilities................................  $    2,469  $     5,023   $    7,785
  Payable to Affymax......................................................          89           --            2
  Deferred revenue........................................................       2,340          396          104
  Current portion of capital lease obligation.............................         187          207          228
                                                                            ----------  -----------  ------------
 
    Total current liabilities.............................................       5,085        5,626        8,119
 
Noncurrent portion of capital lease obligation............................         948          741          619
 
Commitments and contingencies
 
Shareholders' equity:
  Convertible Preferred Stock, no par value; 27,500,000 shares authorized;
    23,166,666 shares issued and outstanding at December 31, 1995 and none
    at December 31, 1996 and June 30, 1997................................      70,439           --           --
  Common stock, no par value; 50,000,000 shares authorized; 536,237,
    22,535,203 and 22,623,987 shares issued and outstanding at December
    31, 1995, 1996 and June 30, 1997, respectively........................       2,717      158,687      158,750
  Note receivable from officer............................................         (42)         (40)         (41)
  Unrealized gain on available-for-sale securities........................         281           49           15
  Deferred compensation...................................................      (2,360)      (1,460)      (1,087)
  Accumulated deficit.....................................................     (32,516)     (44,743)     (54,875)
                                                                            ----------  -----------  ------------
    Total shareholders' equity............................................      38,519      112,493      102,762
                                                                            ----------  -----------  ------------
                                                                            $   44,552  $   118,860   $  111,500
                                                                            ----------  -----------  ------------
                                                                            ----------  -----------  ------------
</TABLE>
 
                             See Accompanying Notes
 
                                      F-3
<PAGE>
                                AFFYMETRIX, INC.
                            STATEMENTS OF OPERATIONS
                    (IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)
 
<TABLE>
<CAPTION>
                                                                                              SIX MONTHS
                                                           YEAR ENDED DECEMBER 31,          ENDED JUNE 30,
                                                      ---------------------------------  ---------------------
                                                        1994        1995        1996       1996        1997
                                                      ---------  ----------  ----------  ---------  ----------
                                                                                              (UNAUDITED)
<S>                                                   <C>        <C>         <C>         <C>        <C>
REVENUE:
  Product...........................................  $      --  $       --  $    1,389  $     457  $    1,362
  Contract and grant................................      1,574       4,625      10,583      3,258       6,188
                                                      ---------  ----------  ----------  ---------  ----------
    Total revenue...................................      1,574       4,625      11,972      3,715       7,550
 
COSTS AND EXPENSES:
  Cost of product revenue...........................         --          --       2,178        707       1,844
  Research and development..........................      9,483      12,420      18,762      8,310      12,710
  General and administrative........................      2,303       3,833       7,569      3,550       5,815
                                                      ---------  ----------  ----------  ---------  ----------
    Total costs and expenses........................     11,786      16,253      28,509     12,567      20,369
                                                      ---------  ----------  ----------  ---------  ----------
    Loss from operations............................    (10,212)    (11,628)    (16,537)    (8,852)    (12,819)
 
    Interest income.................................        575       1,301       4,416      1,208       2,732
    Interest expense................................        (43)       (420)       (106)       (54)        (45)
                                                      ---------  ----------  ----------  ---------  ----------
    Net loss........................................  $  (9,680) $  (10,747) $  (12,227) $  (7,698) $  (10,132)
                                                      ---------  ----------  ----------  ---------  ----------
                                                      ---------  ----------  ----------  ---------  ----------
    Historical net loss per share...................                                                $    (0.45)
                                                                                                    ----------
                                                                                                    ----------
    Shares used in computing historical net loss per
      share.........................................                                                    22,594
                                                                                                    ----------
                                                                                                    ----------
    Pro forma net loss per share....................  $   (0.55) $    (0.61) $    (0.61) $   (0.43)
                                                      ---------  ----------  ----------  ---------
                                                      ---------  ----------  ----------  ---------
    Shares used in computing pro forma net loss per
      share.........................................     17,653      17,664      20,131     17,782
                                                      ---------  ----------  ----------  ---------
                                                      ---------  ----------  ----------  ---------
</TABLE>
 
                             See Accompanying Notes
 
                                      F-4
<PAGE>
                                AFFYMETRIX, INC.
                       STATEMENTS OF SHAREHOLDERS' EQUITY
                      (IN THOUSANDS, EXCEPT SHARE AMOUNTS)
<TABLE>
<CAPTION>
                                                    CONVERTIBLE
                                                     PREFERRED      COMMON     NOTE RECEIVABLE   UNREALIZED       DEFERRED
                                                       STOCK         STOCK      FROM OFFICER    GAIN/ (LOSS)    COMPENSATION
                                                    ------------  -----------  ---------------  -------------  ---------------
<S>                                                 <C>           <C>          <C>              <C>            <C>
Balance, December 31, 1993........................   $   31,283    $     100      $     (80)      $      --       $      --
  Issuance of 74,200 shares of Common Stock upon
    exercise of stock options.....................           --           22             --              --              --
  Interest accrued on notes receivable from
    officers......................................           --           --             (4)             --              --
  Unrealized loss on available-for-sale
    securities....................................           --           --             --            (382)             --
  Net loss........................................           --           --             --              --              --
                                                    ------------  -----------        ------          ------    ---------------
Balance, December 31, 1994........................       31,283          122            (84)           (382)             --
                                                    ------------  -----------        ------          ------    ---------------
  Issuance of 7,333,333 shares of Series B Senior
    Convertible Preferred Stock for cash, net of
    issuance costs................................       32,836           --             --              --              --
  Conversion of note payable to Affymax into
    1,333,333 shares of Series B Senior
    Convertible Preferred Stock...................        6,000           --             --              --              --
  Issuance of 62,749 shares of Common Stock for
    cash upon exercise of stock options...........           --           23             --              --              --
  Issuance of 65,320 shares of Common Stock for
    financing commissions.........................           --           44             --              --              --
  Issuance of warrants to Affymax for 202,441
    shares of Series 2 Subordinated Convertible
    Preferred Stock in lieu of interest...........          320           --             --              --              --
  Interest received on notes receivable from
    officer.......................................           --           --              2              --              --
  Reclassification of notes receivable from
    officers to other assets......................           --           --             40              --              --
  Compensation from accelerated options...........           --           40             --              --              --
  Deferred compensation related to grant of stock
    options.......................................           --        2,488             --              --          (2,488)
  Amortization of deferred compensation...........           --           --             --              --             128
  Unrealized gain on available-for-sale
    securities....................................           --           --             --             663              --
  Net loss........................................           --           --             --              --              --
                                                    ------------  -----------        ------          ------    ---------------
Balance, December 31, 1995........................       70,439        2,717            (42)            281          (2,360)
                                                    ------------  -----------        ------          ------    ---------------
  Issuance of 215,945 shares of Common Stock upon
    exercise of stock options.....................           --          127             --              --              --
  Conversion of 23,166,166 shares of Preferred
    Stock to 15,629,991 shares of Common Stock....      (70,119)      70,119             --              --              --
  Conversion of warrants to purchase 202,441
    shares of Series 2 Subordinated Convertible
    Preferred Stock to warrants to purchase
    134,961 shares of Common Stock................         (320)         320             --              --              --
  Issuance of 6,153,000 shares of Common Stock,
    net of issuance costs and commissions.........           --       85,069             --              --              --
  Interest received on notes receivable from
    officer.......................................           --           --              2              --              --
  Deferred compensation related to grant of stock
    options.......................................           --          335             --              --            (335)
  Amortization of deferred compensation...........           --           --             --              --           1,235
  Unrealized loss on available-for-sale
    securities....................................           --           --             --            (232)             --
  Net loss........................................           --           --             --              --              --
                                                    ------------  -----------        ------          ------    ---------------
Balance, December 31, 1996........................           --      158,687            (40)             49          (1,460)
                                                    ------------  -----------        ------          ------    ---------------
  Issuance of 88,784 shares of Common Stock upon
    exercise of stock options (unaudited).........           --           63             --              --              --
  Interest received on notes receivable from
    officer (unaudited)...........................           --           --             (1)             --              --
  Amortization of deferred compensation
    (unaudited)...................................           --           --             --              --             373
  Unrealized loss on available-for-sale securities
    (unaudited)...................................           --           --             --             (34)             --
  Net loss (unaudited)............................           --           --             --              --              --
                                                    ------------  -----------        ------          ------    ---------------
Balance, June 30, 1997 (unaudited)................   $       --    $ 158,750      $     (41)      $      15       $  (1,087)
                                                    ------------  -----------        ------          ------    ---------------
                                                    ------------  -----------        ------          ------    ---------------
 
<CAPTION>
                                                                         TOTAL
                                                     ACCUMULATED     SHAREHOLDERS'
                                                       DEFICIT          EQUITY
                                                    --------------  ---------------
<S>                                                 <C>             <C>
Balance, December 31, 1993........................    $  (12,089)     $    19,214
  Issuance of 74,200 shares of Common Stock upon
    exercise of stock options.....................            --               22
  Interest accrued on notes receivable from
    officers......................................            --               (4)
  Unrealized loss on available-for-sale
    securities....................................            --             (382)
  Net loss........................................        (9,680)          (9,680)
                                                    --------------  ---------------
Balance, December 31, 1994........................       (21,769)           9,170
                                                    --------------  ---------------
  Issuance of 7,333,333 shares of Series B Senior
    Convertible Preferred Stock for cash, net of
    issuance costs................................            --           32,836
  Conversion of note payable to Affymax into
    1,333,333 shares of Series B Senior
    Convertible Preferred Stock...................            --            6,000
  Issuance of 62,749 shares of Common Stock for
    cash upon exercise of stock options...........            --               23
  Issuance of 65,320 shares of Common Stock for
    financing commissions.........................            --               44
  Issuance of warrants to Affymax for 202,441
    shares of Series 2 Subordinated Convertible
    Preferred Stock in lieu of interest...........            --              320
  Interest received on notes receivable from
    officer.......................................            --                2
  Reclassification of notes receivable from
    officers to other assets......................            --               40
  Compensation from accelerated options...........            --               40
  Deferred compensation related to grant of stock
    options.......................................            --               --
  Amortization of deferred compensation...........            --              128
  Unrealized gain on available-for-sale
    securities....................................            --              663
  Net loss........................................       (10,747)         (10,747)
                                                    --------------  ---------------
Balance, December 31, 1995........................       (32,516)          38,519
                                                    --------------  ---------------
  Issuance of 215,945 shares of Common Stock upon
    exercise of stock options.....................            --              127
  Conversion of 23,166,166 shares of Preferred
    Stock to 15,629,991 shares of Common Stock....            --               --
  Conversion of warrants to purchase 202,441
    shares of Series 2 Subordinated Convertible
    Preferred Stock to warrants to purchase
    134,961 shares of Common Stock................            --               --
  Issuance of 6,153,000 shares of Common Stock,
    net of issuance costs and commissions.........            --           85,069
  Interest received on notes receivable from
    officer.......................................            --                2
  Deferred compensation related to grant of stock
    options.......................................            --               --
  Amortization of deferred compensation...........            --            1,235
  Unrealized loss on available-for-sale
    securities....................................            --             (232)
  Net loss........................................       (12,227)         (12,227)
                                                    --------------  ---------------
Balance, December 31, 1996........................       (44,743)         112,493
                                                    --------------  ---------------
  Issuance of 88,784 shares of Common Stock upon
    exercise of stock options (unaudited).........            --               63
  Interest received on notes receivable from
    officer (unaudited)...........................            --               (1)
  Amortization of deferred compensation
    (unaudited)...................................            --              373
  Unrealized loss on available-for-sale securities
    (unaudited)...................................            --              (34)
  Net loss (unaudited)............................       (10,132)         (10,132)
                                                    --------------  ---------------
Balance, June 30, 1997 (unaudited)................    $  (54,875)     $   102,762
                                                    --------------  ---------------
                                                    --------------  ---------------
</TABLE>
 
                             See Accompanying Notes
 
                                      F-5
<PAGE>
                                AFFYMETRIX, INC.
                            STATEMENTS OF CASH FLOWS
                                 (IN THOUSANDS)
 
<TABLE>
<CAPTION>
                                                                                                 SIX MONTHS ENDED
                                                                  YEAR ENDED DECEMBER 31,            JUNE 30,
                                                              -------------------------------  --------------------
                                                                1994       1995       1996       1996       1997
                                                              ---------  ---------  ---------  ---------  ---------
                                                                                                   (UNAUDITED)
<S>                                                           <C>        <C>        <C>        <C>        <C>
CASH FLOWS FROM OPERATING ACTIVITIES:
  Net loss..................................................  $  (9,680) $ (10,747) $ (12,227) $  (7,698) $ (10,132)
  Adjustments to reconcile net loss to net cash used in
    operating activities:
    Depreciation and amortization...........................        689        701      1,286        579        881
    Amortization of deferred compensation...................         --        128      1,235        618        373
    Other...................................................        565        357       (518)      (575)       206
    Changes in operating assets and liabilities:
      Accounts receivable...................................        (90)    (1,252)      (546)        77     (2,592)
      Inventories...........................................         --       (670)    (1,231)      (880)      (137)
      Other assets..........................................        560       (252)      (292)      (392)      (687)
      Accounts payable and other accrued liabilities........        295      1,263        945      1,033      2,222
      Accrued warranty......................................         --        160      1,609        200        540
      Payable to Affymax....................................     (1,320)      (165)       (89)       (80)         2
      Deferred revenue......................................      1,627        253     (1,944)      (322)      (292)
                                                              ---------  ---------  ---------  ---------  ---------
        Net cash used in operating activities...............     (7,354)   (10,224)   (11,772)    (7,440)    (9,616)
                                                              ---------  ---------  ---------  ---------  ---------
CASH FLOWS FROM INVESTING ACTIVITIES:
  Capital expenditures......................................     (1,207)    (2,283)    (3,488)    (1,236)    (4,443)
  Proceeds from sale of available-for-sale securities.......      5,308      8,538     48,417     12,460     66,364
  Proceeds from maturities of available-for-sale
    securities..............................................         --      5,485     42,859      2,157     12,252
  Purchases of available-for-sale securities................     (2,990)   (38,428)  (149,363)   (70,383)   (44,068)
                                                              ---------  ---------  ---------  ---------  ---------
        Net cash provided by (used in) investing
          activities........................................      1,111    (26,688)   (61,575)   (57,002)    30,105
                                                              ---------  ---------  ---------  ---------  ---------
CASH FLOWS FROM FINANCING ACTIVITIES:
  Issuances of Common Stock, net............................         22         23     85,196     83,362         63
  Issuances of Preferred Stock, net.........................         --     32,880         --         --         --
  Proceeds from capital lease obligation....................      1,307         --         --         --         --
  Principal payments on capital lease obligation............         (3)      (169)      (187)       (92)      (101)
  Issuance of convertible note payable to Affymax...........      6,000         --         --         --         --
  Principal payments on notes payable.......................       (819)        --         --         --         --
                                                              ---------  ---------  ---------  ---------  ---------
        Net cash provided (used in) by financing
          activities........................................      6,507     32,734     85,009     83,270        (38)
                                                              ---------  ---------  ---------  ---------  ---------
        Net increase (decrease) in cash and cash
          equivalents.......................................        264     (4,178)    11,662     18,828     20,451
  Cash and cash equivalents at beginning of period..........      6,395      6,659      2,481      2,481     14,143
                                                              ---------  ---------  ---------  ---------  ---------
  Cash and cash equivalents at end of period................  $   6,659  $   2,481  $  14,143  $  21,309  $  34,594
                                                              ---------  ---------  ---------  ---------  ---------
                                                              ---------  ---------  ---------  ---------  ---------
SUPPLEMENTAL DISCLOSURE OF NONCASH FINANCING ACTIVITIES:
  Conversion of note payable and contributions from Affymax
    to Preferred Stock......................................  $      --  $   6,000  $      --  $      --  $      --
                                                              ---------  ---------  ---------  ---------  ---------
                                                              ---------  ---------  ---------  ---------  ---------
  Assets purchased under capital lease obligation...........  $   1,297  $      --  $      --  $      --  $      --
                                                              ---------  ---------  ---------  ---------  ---------
                                                              ---------  ---------  ---------  ---------  ---------
</TABLE>
 
                             See Accompanying Notes
 
                                      F-6
<PAGE>
                                AFFYMETRIX, INC.
 
                         NOTES TO FINANCIAL STATEMENTS
 
   (INFORMATION FOR THE SIX MONTHS ENDED JUNE 30, 1996 AND 1997 IS UNAUDITED)
 
NOTE 1--NATURE OF OPERATIONS
 
    Affymetrix, Inc. ("Affymetrix" or the "Company") is focused on developing
GeneChip-Registered Trademark- based products and related technology for the
acquisition, analysis, and management of complex genetic data. The business and
operations of Affymetrix commenced in 1991 by Affymax N.V. and subsidiaries
("Affymax") and were initially conducted within Affymax. In March 1992,
Affymetrix was incorporated as a California corporation and became a wholly
owned subsidiary of Affymax. Beginning in September 1993, Affymetrix issued
equity securities which diluted Affymax' shareholding in Affymetrix. In March
1995, Glaxo plc, now Glaxo Wellcome plc ("Glaxo"), purchased Affymax, including
its then 65% interest in Affymetrix. Affymax owned approximately 46% of
Affymetrix on December 31, 1995. Glaxo owns approximately 33% of Affymetrix at
December 31, 1996. Through March 31, 1996, the Company was in the development
stage. In April 1996, the Company commenced commercial sales of the GeneChip
system and an HIV probe array for research use. Therefore the Company is no
longer considered to be in the development stage.
 
    Affymetrix' success will depend on timely development and market acceptance
of new products, the impact of competitive products and technological change,
the impact of intellectual property, limited manufacturing capability and sole
source providers, and dependence on collaborative partners. The factors that
could affect the performance of the Company are more fully described elsewhere
in this Prospectus. Actual results could differ materially from those
anticipated in any forward-looking statements, and Affymetrix does not undertake
any obligation to publicly release the result of any revisions to the
forward-looking statements that may be made to reflect events or circumstances
after the date hereof or to reflect the occurrence of any unanticipated events.
 
NOTE 2--SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
 
    The summary of significant accounting policies is presented to assist the
reader in understanding and evaluating the financial statements. These policies
are in conformity with generally accepted accounting principles. Certain amounts
for prior years have been reclassified to conform to current year presentation.
 
  INTERIM FINANCIAL INFORMATION
 
    The financial statements for the six months ended June 30, 1996 and 1997 are
unaudited but include all adjustments (consisting of normal recurring entries)
which the Company considers necessary for fair presentation. Operating results
for the six months ended June 30, 1997 are not necessarily indicative of the
results that may be expected for any future periods.
 
  USE OF ESTIMATES
 
    The preparation of the financial statements in conformity with generally
accepted accounting principles requires management to make estimates and
assumptions that affect amounts reported in the financial statements and
accompanying notes. Actual results could differ from those estimates.
 
  REVENUE RECOGNITION
 
    Contract and grant revenue is recorded as earned as defined within the
specific agreements. Payments received in advance under these arrangements are
recorded as deferred revenue until
 
                                      F-7
<PAGE>
                                AFFYMETRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
   (INFORMATION FOR THE SIX MONTHS ENDED JUNE 30, 1996 AND 1997 IS UNAUDITED)
 
NOTE 2--SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
earned. Direct costs associated with these contracts and grants are reported as
research and development expense. Revenue for product shipment during the
development stage are recorded as contract revenue pursuant to the development
agreements. The Company recognizes product revenue from the sale of its products
upon shipment to its customers. Reserves are provided for anticipated product
returns and warranty expenses at the time of shipment.
 
    Revenue from customers representing 10% or more of total contract and grant
revenue during fiscal 1994, 1995 and 1996 and for the six months ended June 30,
1996 and 1997 is as follows:
 
<TABLE>
<CAPTION>
                                                                  YEAR ENDED                  SIX MONTHS
                                                                 DECEMBER 31,               ENDED JUNE 30,
                                                        -------------------------------  --------------------
                                                          1994       1995       1996       1996       1997
                                                        ---------  ---------  ---------  ---------  ---------
CUSTOMER:
<S>                                                     <C>        <C>        <C>        <C>        <C>
    A.................................................     --            25%        18%        34%        32%
    B.................................................     --            23%        18%        17%     --
    C.................................................     --            22%        15%        10%     --
    D.................................................        54%        17%        19%        29%        22%
    E.................................................        29%     --         --         --         --
    F.................................................     --         --         --         --            22%
</TABLE>
 
    There were no product sales for the years ended December 31, 1994 and 1995.
Product sales were approximately $1.4 million in the year ended December 31,
1996 and $457,000 and $1.4 million for the six months ended June 30, 1996 and
1997, respectively.
 
  RESEARCH AND DEVELOPMENT
 
    Research and development expenses consist of costs incurred for internal,
contract and grant-sponsored research and development. These costs include
direct and research-related overhead expenses.
 
  NET LOSS PER SHARE
 
    Except as noted below, historical net loss per share is computed using the
weighted average number of common shares outstanding. Common equivalent shares
are excluded from the computation as their effect is antidilutive, except that,
pursuant to the Securities and Exchange Commission ("SEC") Staff Accounting
Bulletins, common and common equivalent shares (stock options, convertible notes
payable, Convertible Preferred Stock, and warrants) issued during the 12 months
prior to the filing of the Company's initial public offering at prices below the
assumed public offering price have been included in the calculation as if they
were outstanding for all periods presented (using the treasury stock method for
stock options and warrants and the if-converted method for Convertible Preferred
Stock).
 
                                      F-8
<PAGE>
                                AFFYMETRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
   (INFORMATION FOR THE SIX MONTHS ENDED JUNE 30, 1996 AND 1997 IS UNAUDITED)
 
NOTE 2--SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
    Historical net loss per share information is as follows:
 
<TABLE>
<CAPTION>
                                               YEAR ENDED DECEMBER 31,               SIX MONTHS ENDED JUNE 30,
                                     --------------------------------------------  -----------------------------
                                         1994           1995            1996           1996            1997
                                     -------------  -------------  --------------  -------------  --------------
<S>                                  <C>            <C>            <C>             <C>            <C>
Net loss per share.................         $(1.24)        $(1.38)         $(0.82)        $(1.07)         $(0.45)
Shares used in computing net loss
  per share........................      7,801,000      7,812,000      14,834,000      7,188,000      22,594,000
</TABLE>
 
    Pro forma per share data is provided to show the calculation on a consistent
basis for the periods presented. It has been computed as described above and
also gives retroactive effect from the date of issuance to the conversion of
Preferred Stock which automatically converted to common shares upon the closing
of the Company's initial public offering.
 
  CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS
 
    Cash equivalents and short-term investments consist of debt securities.
Management determines the appropriate classification of debt securities at the
time of purchase. As of June 30, 1997, Affymetrix' debt securities are
classified as available-for-sale and are carried at fair value with unrealized
gains and losses reported in shareholders' equity. Affymetrix reports all liquid
securities with maturities at date of purchase of three months or less that are
readily convertible into cash and have insignificant interest rate risk as cash
equivalents. All other available-for-sale securities are recorded as short-term
investments. The cost of debt securities is adjusted for amortization of
premiums and discounts to maturity. This amortization is included in interest
income. Realized gains and losses on available-for-sale securities are included
in interest income. The cost of securities sold is based on the specific
identification method. Interest and dividends on securities classified as
available-for-sale are included in interest income. The fair values of
securities are based on quoted market prices.
 
  INVENTORIES
 
    Inventories are stated at the lower of cost, as determined by the first-in,
first-out method, or market and consist entirely of finished goods at December
31, 1995 and of $358,000 of raw materials, $178,000 of work-in-progress and $1.4
million of finished goods at December 31, 1996 and of $579,000 of raw materials,
$79,000 of work-in-progress and $1.4 million of finished goods at June 30, 1997.
 
  PROPERTY AND EQUIPMENT
 
    The costs of property and equipment, including equipment under capital
leases, are depreciated for financial reporting purposes using the straight-line
method over the estimated useful lives of the assets ranging from two to five
years. Leasehold improvements are amortized over the useful lives of the assets
or the lease-term, whichever is shorter.
 
                                      F-9
<PAGE>
                                AFFYMETRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
   (INFORMATION FOR THE SIX MONTHS ENDED JUNE 30, 1996 AND 1997 IS UNAUDITED)
 
NOTE 2--SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
  ACCOUNTS PAYABLE AND ACCRUED LIABILITIES
 
    Accounts payable and accrued liabilities consist of the following (in
thousands):
 
<TABLE>
<CAPTION>
                                                               DECEMBER 31,         JUNE 30,
                                                           --------------------  --------------
                                                             1995       1996          1997
                                                           ---------  ---------  --------------
                                                                                  (UNAUDITED)
<S>                                                        <C>        <C>        <C>
Accounts payable.........................................  $     928  $   1,284    $    3,169
Accrued compensation and related.........................        576        445           629
Accrued warranty.........................................        160      1,769         2,309
Collaborative research refund............................        360        450           450
Other....................................................        445      1,075         1,228
                                                           ---------  ---------       -------
    Total................................................  $   2,469  $   5,023    $    7,785
                                                           ---------  ---------       -------
                                                           ---------  ---------       -------
</TABLE>
 
  STOCK BASED COMPENSATION
 
    In October 1995, the Financial Accounting Standards Board issued "Accounting
for Stock-Based Compensation" ("Statement No. 123") which is effective for
fiscal 1996. Under Statement No. 123, stock-based compensation expense is
measured using either the intrinsic-value method as prescribed in APB Opinion
No. 25 or the fair value method described in Statement No. 123. Affymetrix has
adopted the disclosure only alternative under Statement No. 123 and,
accordingly, Affymetrix has disclosed the pro forma net income or loss and per
share amounts in the notes to the financial statements using the fair value
based method.
 
  CONCENTRATIONS OF RISK
 
    Cash equivalents and investments are financial instruments which potentially
subject Affymetrix to concentrations of risk to the extent of amounts recorded
in the Balance Sheet. Corporate policy restricts the amount of credit exposure
to any one issuer and to any one type of investment, other than securities
issued by the United States Government.
 
NOTE 3--COLLABORATIVE AGREEMENTS AND GRANTS
 
    The Company has agreements with several entities to develop and test probe
arrays for the detection of certain gene sequences, mutations or organisms.
Under such agreements, the Company is typically paid a development fee and may
receive milestone payments upon achievement of certain technical goals. The
Company also has research agreements with several universities and research
organizations. The Company generally obtains rights to intellectual property
arising from these agreements. If a project is successful, the Company and the
third-party collaborator would negotiate the right to commercialize products
resulting from such project. The Company has received a substantial portion of
its revenues since inception from its collaborative partners and intends to
enter into collaborative arrangements with other companies to apply its
technology, fund development, commercialize potential future products, and
assist in obtaining regulatory approval. Total costs incurred under contract and
grant arrangements for the years ended December 31, 1994, 1995, and 1996 were
approximately $1.5 million, $5.2 million, and $8.8 million, respectively, and
$4.2 million and $7.0 million for the six months ended June 30, 1996 and 1997,
respectively, and are included in research and development expenses.
 
                                      F-10
<PAGE>
                                AFFYMETRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
   (INFORMATION FOR THE SIX MONTHS ENDED JUNE 30, 1996 AND 1997 IS UNAUDITED)
 
NOTE 3--COLLABORATIVE AGREEMENTS AND GRANTS (CONTINUED)
    In April 1997, Bristol-Myers Squibb Company, Millennium Pharmaceuticals Inc.
and Affymetrix entered into a corporate consortium to fund a five-year research
program in functional genomics at the Whitehead Institute/MIT Center for Genome
Research. The new program, under the direction of Dr. Eric S. Lander, the
Director of the Whitehead Institute, will develop tools and strategies to trace
the origin of genetic diseases, investigate DNA sequence variation and correlate
patterns of gene activity with cellular processes and disease. In return for
enabling this research, the Company will receive certain licensing rights to
developments funded by the consortium.
 
    In November 1996, Incyte Pharmaceuticals, Inc. ("Incyte") and the Company
entered into a joint program to develop and commercialize novel and
disease-specific gene expression databases and services. This agreement is an
expansion of a feasibility agreement initiated in April 1996. Under the terms of
the agreement, novel and disease-specific genes will be selected from Incyte's
LifeSeq-TM- genomic databases to generate DNA probe arrays using the Affymetrix
GeneChip system. The resulting LifeChip products will allow the generation of
information on the preselected genes across biological specimens to identify
molecules and expression patterns associated with human disease. Initially,
probe arrays derived from LifeSeq information will be designed for use in such
fields as prostate and breast cancer, inflammation, and G-protein coupled
receptor pathways. The Company and Incyte will share all profits and co-own the
intellectual property generated under the collaboration.
 
    In September 1996, bioMerieux Vitek, Inc. ("bioMerieux") and the Company
executed a collaboration agreement to develop DNA probe arrays using the
Affymetrix GeneChip technology for clinical diagnostic kits for bacterial
identification and antibiotic resistance analysis. The agreement provides for
certain research funding, license and milestone payments. bioMerieux will also
fund certain research activities at the Company for a minimum of three years.
Additionally, a manufacturing agreement was signed under which the Company will
manufacture GeneChip probe arrays for sale to bioMerieux. The agreement provides
for royalties to the Company on bioMerieux' sales of GeneChip probe arrays.
 
    In September 1996, OncorMed, Inc. ("OncorMed") and the Company entered into
an agreement to collaborate in the development and clinical validation of
genetic testing services using the Affymetrix GeneChip system for analysis of
genes associated with cancer. The collaborative effort will begin with the p53
gene and may include genes involved with breast, colon, ovarian and other
cancers.
 
    In December 1995, the Company and Genetics Institute entered into a supply
agreement under which the Company agreed to manufacture and supply custom probe
arrays based on specific genes identified and selected by Genetics Institute.
Pursuant to the agreement, the Company is obligated to develop custom probe
arrays until February 1998 and to supply certain minimum quantities of custom
probe arrays developed for Genetics Institute until February 2001. The Company
will receive fees for the design and delivery of the custom probe arrays, and
may receive milestone payments and royalties on certain therapeutic compounds if
discovered by Genetics Institute using these probe arrays.
 
    Pursuant to an earlier collaboration agreement with Genetics Institute
entered into in November 1994, Genetics Institute provided research funding to
the Company for the development of DNA probe arrays to enable Genetics Institute
to discover new genes and uses for genes. The Company has completed performance
of the 1994 agreement and, accordingly, development funding under the
collaboration agreement has been discontinued. Affymetrix has agreed to supply
custom probe arrays developed under the collaboration agreement to Genetics
Institute in accordance with the supply agreement. Genetics Institute has all
rights to therapeutic compounds discovered through the use of DNA probe arrays
provided by the Company, and the Company will receive royalties and milestone
 
                                      F-11
<PAGE>
                                AFFYMETRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
   (INFORMATION FOR THE SIX MONTHS ENDED JUNE 30, 1996 AND 1997 IS UNAUDITED)
 
NOTE 3--COLLABORATIVE AGREEMENTS AND GRANTS (CONTINUED)
payments on certain therapeutic compounds. The Company retains rights to
enhancements to the GeneChip system technology developed in the collaboration.
The Company and Genetics Institute are negotiating amendments to their existing
agreements.
 
    In August 1995, the Company was awarded a three-year grant from the National
Institutes of Health ("NIH") National Center for Human Genome Research for
approximately $6.0 million. As of June 30, 1997 the Company has recognized $2.3
million in revenue related to the grant, and the remaining amounts are subject
to appropriation by the NIH.
 
    In November 1994, the Company entered into a collaborative agreement with
Hewlett-Packard Company ("HP") to combine the Affymetrix GeneChip technology and
HP's measurement and instrument capabilities to develop and manufacture a more
advanced scanner for use with GeneChip probe arrays. In exchange for certain
rights, the Company received and would receive certain payments, including
milestone payments, as defined research and development objectives are achieved.
The Company expects that HP will be the sole source for its scanners. In
February 1997, the Company and HP announced the availability of HP's GeneArray
scanner as a part of the Affymetrix GeneChip system. The Company and HP also
redefined their 1994 business alliance. Under the terms of the revised
agreement, the Company has re-acquired all marketing rights for its GeneChip
products and has expanded its right to sell the HP GeneArray scanner as part of
the Affymetrix GeneChip system to all potential markets.
 
    In November 1994, the Company received a license payment from HP of $1.2
million that was classified as deferred revenue at December 31, 1995. Due to the
expiration of certain restrictions, this amount was recognized as contract and
grant revenue in November 1996.
 
    In October 1994, the Company and Molecular Dynamics, Inc. ("Molecular
Dynamics") were awarded a five-year matching grant for a total of $31.5 million
under the Advanced Technology Program within the National Institute of Standards
and Technology to develop a miniaturized DNA diagnostic device, of which
approximately $10.7 million will be available to Molecular Dynamics. The
contract provides that the Company will receive matching funding up to $20.8
million, some of which will be used to fund activities at collaborating academic
institutions. The award is subject to yearly congressional authorization, which
is uncertain. The Company expects to receive payments monthly based on costs
incurred. As of June 30, 1997 the Company has recognized revenue of $5.3 million
related to this grant.
 
NOTE 4--AVAILABLE-FOR-SALE SECURITIES
 
    The following is a summary of available-for-sale securities as of December
31, 1995 (in thousands):
 
<TABLE>
<CAPTION>
                                                             GROSS UNREALIZED      GROSS UNREALIZED     ESTIMATED FAIR
                                                   COST            GAINS                LOSSES              VALUE
                                                 ---------  -------------------  ---------------------  --------------
<S>                                              <C>        <C>                  <C>                    <C>
U.S. Government obligations....................  $  38,115       $     309             $      27          $   38,397
                                                 ---------           -----                   ---        --------------
                                                 ---------           -----                   ---        --------------
Amounts included in:
  Cash equivalents.............................  $   1,995       $  --                 $  --              $    1,995
  Short-term investments.......................     36,120             309                    27              36,402
                                                 ---------           -----                   ---        --------------
    Total securities...........................  $  38,115       $     309             $      27          $   38,397
                                                 ---------           -----                   ---        --------------
                                                 ---------           -----                   ---        --------------
</TABLE>
 
                                      F-12
<PAGE>
                                   AFFYMETRIX
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
   (INFORMATION FOR THE SIX MONTHS ENDED JUNE 30, 1996 AND 1997 IS UNAUDITED)
 
NOTE 4--AVAILABLE-FOR-SALE SECURITIES (CONTINUED)
 
    The following is a summary of available-for-sale securities as of December
31, 1996 (in thousands):
 
<TABLE>
<CAPTION>
                                                             GROSS UNREALIZED      GROSS UNREALIZED     ESTIMATED FAIR
                                                  COST             GAINS                LOSSES              VALUE
                                               -----------  -------------------  ---------------------  --------------
<S>                                            <C>          <C>                  <C>                    <C>
U.S. Government obligations..................  $    88,758       $     134             $      86         $     88,806
U.S. Corporate securities....................       17,017               9                     8               17,018
                                               -----------           -----                   ---        --------------
  Total securities...........................  $   105,775       $     143             $      94         $    105,824
                                               -----------           -----                   ---        --------------
                                               -----------           -----                   ---        --------------
Amounts included in:
  Cash equivalents...........................  $    10,985       $  --                 $  --             $     10,985
  Short-term investments.....................       94,790             143                    94               94,839
                                               -----------           -----                   ---        --------------
    Total securities.........................  $   105,775       $     143             $      94         $    105,824
                                               -----------           -----                   ---        --------------
                                               -----------           -----                   ---        --------------
</TABLE>
 
    The realized gains and losses on sales of available-for-sale securities were
immaterial for the years ended December 31, 1995 and 1996 and the six months
ended June 30, 1996 and 1997.
 
    The following is a summary of the contractual maturity of available-for-sale
securities at December 31, 1996 (in thousands):
 
<TABLE>
<CAPTION>
                                                                                ESTIMATED FAIR
                                                                                    VALUE
                                                                                --------------
<S>                                                                             <C>
Mature in one year or less....................................................   $     59,544
Mature after one year through three years.....................................         46,280
                                                                                --------------
  Total.......................................................................   $    105,824
                                                                                --------------
                                                                                --------------
</TABLE>
 
NOTE 5--RELATED PARTY TRANSACTIONS
 
    In December 1994, the Company issued a $6.0 million subordinated convertible
promissory note to Affymax. In August of 1995, the note was converted into
1,333,333 shares of Series B Senior Convertible Preferred Stock issued at $4.50
per share. The Company also exercised an option to satisfy interest due on the
note through July 1995, amounting to $319,856, by issuing Affymax five-year
warrants to purchase 202,441 shares of Series 2 Subordinated Convertible
Preferred Stock at $5.50 per share. In connection with the Company's initial
public offering, the Preferred Stock converted to 888,888 shares of Common Stock
and the warrants converted to warrants to purchase 134,960 shares of Common
Stock at $8.25 per share.
 
    Affymetrix and Affymax are parties to a technology license agreement whereby
the Company retains an exclusive worldwide royalty-free license from Affymax to
certain technology and to certain future inventions in diagnostics and research
supply markets. In February 1997, the Company and Affymax, as well as certain
Affymax and Glaxo affiliates, entered into a revised technology agreement. Under
the terms of the agreement, the Affymax entities assigned all rights in their
light directed synthesis technology patents to the Company and canceled their
prior agreements relating to technology licensing and the Company relinquished
its licenses to certain technologies including encoded synthetic libraries.
 
                                      F-13
<PAGE>
                                   AFFYMETRIX
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
   (INFORMATION FOR THE SIX MONTHS ENDED JUNE 30, 1996 AND 1997 IS UNAUDITED)
 
NOTE 5--RELATED PARTY TRANSACTIONS (CONTINUED)
    Two directors of the Company are each employees of a subsidiary of Glaxo.
 
    The Company received legal services from Townsend and Townsend and Crew LLP
("Townsend") related to the intellectual property rights of the Company. A
partner of Townsend was also an employee of the Company on a part time basis
through January 1996, and became a full time employee thereafter. Legal expenses
related to services performed by Townsend were approximately $369,000 in 1994,
$612,000 in 1995 and $793,000 in 1996.
 
    In December 1994, in connection with a lease agreement between Affymetrix
and a third party, Affymax, with approval of the third party lessor, agreed to
release the Company from certain financial covenants to the third party. In
exchange for this release, the Company issued a five-year warrant to Affymax to
purchase 103,382 shares of Series 2 Subordinated Convertible Preferred Stock at
$5.50 per share. In connection with the Company's initial public offering, the
warrant was converted to a warrant to buy 68,921 shares of Common Stock at $8.25
per share.
 
NOTE 6--COMMITMENTS
 
  CAPITAL LEASES
 
    In December 1994, the Company entered into a financing arrangement with a
leasing company for existing equipment. Under the terms of the lease, the
Company received a single minimum aggregate lease payment of $1.3 million at the
inception of the lease. The leaseback contract includes a five-year term
expiring January 2, 2000, with an option to purchase the equipment at the
greater of the residual value or fair market value. Under certain provisions,
the lease may be extended for an additional year. The amount included in
property and equipment related to the lease is $1.2 million with accumulated
depreciation of $0.8 million at December 31, 1995 and $1.2 million at December
31, 1996 and at June 30, 1997. Amortization of this property and equipment is
included in depreciation expense.
 
  OPERATING LEASES
 
    Since January 1, 1993, the Company has been occupying a research facility in
Santa Clara, California originally leased to Affymax. In February 1994, the
Company entered into an operating sublease agreement with Affymax for a 33 month
period. Amounts expensed under this agreement are approximately $472,000 in
1994, $529,000 in 1995 and $534,000 in 1996. In May 1996, the Company canceled
the sublease with Affymax and is now directly leasing the facility from a third
party.
 
    In December 1994, the Company entered into a five-year lease for the rental
of a manufacturing facility in Sunnyvale, California. The Company has options to
renew the lease for two additional three-year terms.
 
    In October 1995, the Company entered into a four-year lease for the rental
of a research and development facility in Sunnyvale, California.
 
    Rent expense related to operating leases was approximately $472,000 in 1994,
$664,000 in 1995 and $950,000 in 1996 and $481,000 and $588,000 for the six
months ended June 30, 1996 and 1997, respectively.
 
                                      F-14
<PAGE>
                                   AFFYMETRIX
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
   (INFORMATION FOR THE SIX MONTHS ENDED JUNE 30, 1996 AND 1997 IS UNAUDITED)
 
NOTE 6--COMMITMENTS (CONTINUED)
    Future minimum lease obligation at December 31, 1996 under all leases are as
follows (in thousands):
 
<TABLE>
<CAPTION>
                                                                           CAPITAL    OPERATING
                                                                           LEASES      LEASES
                                                                          ---------  -----------
<S>                                                                       <C>        <C>
1997....................................................................  $     292   $   1,543
1998....................................................................        292       1,706
1999....................................................................        291       1,816
2000....................................................................        280       1,292
2001....................................................................         --       1,228
Thereafter..............................................................         --       2,047
                                                                          ---------  -----------
    Total minimum lease payments........................................      1,155   $   9,632
                                                                                     -----------
                                                                                     -----------
Less amount representing interest.......................................       (207)
                                                                          ---------
Present value of minimum lease payments.................................        948
Less current portion....................................................       (207)
                                                                          ---------
    Noncurrent obligation under capital lease...........................  $     741
                                                                          ---------
                                                                          ---------
</TABLE>
 
NOTE 7--SHAREHOLDERS' EQUITY
 
  PREFERRED SHARES
 
    In March 1996, the Board authorized the filing of a registration statement
with the Securities and Exchange Commission permitting the Company to sell
shares of its Common Stock to the public. Also, the Board of Directors approved
a two-for-three reverse stock split of its Common Stock through an amendment to
its Articles of Incorporation which was effective on May 20, 1996. As a result,
all of the then outstanding Preferred Stock automatically converted into
15,629,991 shares of Common Stock at the completion of the initial public
offering in June 1996. All common share and per share amounts have been
retroactively adjusted to reflect this event. The conversion rates for the
various issues of Preferred Stock have been retroactively adjusted to reflect
the reverse stock split as well as an anti-dilution adjustment, where required.
Each share of Series A, Series B and Series 1 Preferred Stock converted into
approximately 0.6823, 0.6667, and 0.6775 shares of Common Stock, respectively,
at the completion of the initial public offering.
 
  COMMON SHARES
 
    The Company's initial public offering on June 6, 1996 generated net proceeds
of approximately $83.0 million from the sale of 6,000,000 shares of Common
Stock. In July 1996, the Company's underwriters purchased 153,000 shares of
Common Stock pursuant to the over-allotment option, for additional net proceeds
of $2.1 million. At December 31, 1996, the total number of shares reserved for
future issuance pursuant to outstanding options and warrants was 3,500,000
shares.
 
                                      F-15
<PAGE>
                                   AFFYMETRIX
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
   (INFORMATION FOR THE SIX MONTHS ENDED JUNE 30, 1996 AND 1997 IS UNAUDITED)
 
NOTE 7--SHAREHOLDERS' EQUITY (CONTINUED)
  STOCK WARRANTS
 
    At December 31, 1996 and June 30, 1997, there were outstanding warrants to
purchase 203,881 shares of Common Stock at $8.25 per share which expire at
various dates beginning December 1999 through July 2000.
 
  STOCK OPTION AND BENEFIT PLANS
 
    In 1993, the Board adopted the Affymetrix 1993 Stock Plan (the "Stock Plan")
under which incentive stock options, nonqualified stock options and purchase
rights may be granted to employees and outside consultants.
 
    Options granted under the Stock Plan expire no later than ten years from the
date of grant. The option price shall be at least 100% of the fair value on the
date of grant (110% in certain circumstances), as determined by the Board of
Directors. Options may be granted with different vesting terms from time to time
but not to exceed five years from the date of grant. As of December 31, 1996, a
total of 3,700,000 shares of Common Stock have been reserved for issuance under
the Stock Plan and 106,400 shares were subject to repurchase by the Company.
 
    In March 1996, the Board adopted the 1996 Nonemployee Directors Stock Option
Plan (the "Directors Plan"). There are 300,000 shares of Common Stock reserved
for issuance under the Directors Plan. Only nonemployee directors of the Company
are eligible to participate in the Directors Plan and only nonstatutory stock
options can be granted.
 
    Activity under the stock plans through December 31, 1996 is as follows:
 
<TABLE>
<CAPTION>
                                                                      OUTSTANDING OPTIONS
                                                                  ---------------------------
                                                                                 WEIGHTED-
                                                                   NUMBER OF   AVERAGE PRICE
                                                                    SHARES       PER SHARE
                                                                  -----------  --------------
<S>                                                               <C>          <C>
 Balance at December 31, 1993...................................      380,749    $     0.30
 
    Options granted.............................................      634,238          0.52
    Options exercised...........................................      (74,200)         0.30
    Options canceled............................................      (38,799)         0.30
                                                                  -----------       -------
 
  Balance at December 31, 1994..................................      901,988          0.47
 
    Options granted.............................................    1,423,917          0.68
    Options exercised...........................................      (62,749)         0.36
    Options canceled............................................     (104,032)         0.43
                                                                  -----------       -------
 
  Balance at December 31, 1995..................................    2,159,124          0.60
 
    Options granted.............................................      309,167         10.26
    Options exercised...........................................     (215,945)         0.59
    Options canceled............................................      (20,403)         0.75
                                                                  -----------       -------
 
  Balance at December 31, 1996..................................    2,231,943    $     0.60
                                                                  -----------       -------
                                                                  -----------       -------
</TABLE>
 
                                      F-16
<PAGE>
                                   AFFYMETRIX
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
   (INFORMATION FOR THE SIX MONTHS ENDED JUNE 30, 1996 AND 1997 IS UNAUDITED)
 
NOTE 7--SHAREHOLDERS' EQUITY (CONTINUED)
    For options granted through June 6, 1996, the Company recognized an
aggregate of $2.8 million as deferred compensation for the excess of the deemed
fair value for financial statement presentation purposes of the Common Stock
issuable on exercise of such options over the exercise price. The deferred
compensation expense is being recognized over the vesting period of the options.
 
    Exercise prices for options outstanding as of December 31, 1996 ranged from
$0.30 to $21.56 per share. The weighted-average contractual life of those
options is 8.42 years as summarized below:
 
<TABLE>
<CAPTION>
                                   OPTIONS OUTSTANDING                     OPTIONS EXERCISABLE
                    --------------------------------------------------  --------------------------
                                   WEIGHTED-AVERAGE       WEIGHTED-                   WEIGHTED-
                                 REMAINING CONTRACTUAL     AVERAGE                     AVERAGE
     RANGE OF                            LIFE           EXERCISE PRICE             EXERCISE PRICE
 EXERCISE PRICES      NUMBER          (IN YEARS)          PER SHARE      NUMBER       PER SHARE
- ------------------  -----------  ---------------------  --------------  ---------  ---------------
<S>                 <C>          <C>                    <C>             <C>        <C>
$     0.300- 0.675    2,009,193             8.42          $    0.609      471,113     $   0.570
      4.800-12.000       52,250             9.30               5.144        3,600         4.800
     12.625-21.563      170,500             8.14              16.196           --            --
- ------------------  -----------              ---        --------------  ---------       -------
$     0.300-21.563    2,231,943             8.42          $    1.935      474,713     $   0.602
- ------------------  -----------              ---        --------------  ---------       -------
- ------------------  -----------              ---        --------------  ---------       -------
</TABLE>
 
  PRO FORMA DISCLOSURE UNDER STATEMENT NO. 123
 
    In accordance with the provisions of Statement No. 123, the Company is
disclosing pro forma information regarding net loss and net loss per share as if
the Company had accounted for its stock based compensation plans under the fair
value method of Statement No. 123.
 
    The fair value of options was estimated at the date of grant using a
Black-Scholes option pricing model with the following assumptions for 1995 and
1996: risk free interest rate of 6.36%; a dividend yield of zero; volatility
factors of the expected market price of the Company's Common Stock price of .53;
and a weighted average expected option term of one year from vested date.
 
    The Black-Scholes option valuation model was developed for use in estimating
the fair value of traded options which have no vesting restrictions and are
fully transferable. In addition, option valuation models require the input of
highly subjective assumptions including the expected stock volatility. Because
the Company's employee stock options have characteristics significantly
different from those of traded options, and because changes in the subjective
input assumptions can materially affect the fair value estimate, in management's
opinion, the existing models do not necessarily provide a reliable single
measure of the fair value of its employee stock options.
 
    The weighted average fair value of options granted during 1995 and 1996 was
$0.30 and $4.72, respectively. For purposes of pro forma disclosures the
estimated fair value of the options in excess of the expense recognized in
conjunction with the amortization of deferred compensation is amortized to
expense over the options' vesting period, generally five years. The pro forma
effect on net loss is not
 
                                      F-17
<PAGE>
                                AFFYMETRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
   (INFORMATION FOR THE SIX MONTHS ENDED JUNE 30, 1996 AND 1997 IS UNAUDITED)
 
NOTE 7--SHAREHOLDERS' EQUITY (CONTINUED)
 
necessarily indicative of potential pro forma effects on results for future
years. The Company's pro forma information as of December 31, 1995 and 1996 is
as follows (in thousands excepts per share amounts):
 
<TABLE>
<CAPTION>
                                                                          1995        1996
                                                                       ----------  ----------
<S>                                                                    <C>         <C>
Pro forma net loss...................................................  $  (10,747) $  (12,345)
                                                                       ----------  ----------
                                                                       ----------  ----------
Pro forma net loss per share.........................................  $    (0.61) $    (0.62)
                                                                       ----------  ----------
                                                                       ----------  ----------
</TABLE>
 
NOTE 8--INCOME TAXES
 
    As of December 31, 1996, the Company has net operating loss carryforwards of
approximately $31.0 million, which will expire at various dates beginning on
2008 through 2011, if not utilized.
 
    Utilization of the net operating losses and credits may be subject to a
substantial annual limitation due to the ownership change limitations provided
by the Internal Revenue Code of 1986. The annual limitation may result in the
expiration of net operating losses and credits before utilization.
 
    Significant components of the Company deferred tax assets as of December 31,
1995 and 1996 are as follows (in thousands):
 
<TABLE>
<CAPTION>
                                                                          1995        1996
                                                                       ----------  ----------
<S>                                                                    <C>         <C>
Net operating loss carryforwards.....................................  $    8,063  $   10,705
Research credits.....................................................       1,167       1,457
Deferred revenue.....................................................       1,041         126
Other-net............................................................         532       2,425
                                                                       ----------  ----------
Total deferred tax assets............................................      10,803      14,713
Valuation allowance for deferred tax assets..........................     (10,803)    (14,713)
                                                                       ----------  ----------
Net deferred tax assets..............................................  $       --  $       --
                                                                       ----------  ----------
                                                                       ----------  ----------
</TABLE>
 
    The valuation allowance increased by $3.7 million, $4.9 million and $3.9
million during 1994, 1995, and 1996, respectively.
 
NOTE 9--CONTINGENCIES
 
    In March 1997, Hyseq Inc. ("Hyseq") filed a suit against the Company in the
United States District Court alleging that the Company infringes United States
patent 5,202,231 and 5,525,464 issued to Drs. Drmanac and Crkvenjakov. In the
opinion of management, the outcome of the action will not have a material
adverse effect on the Company's financial position.
 
    The Company routinely receives communications from third parties asserting
patent or other rights covering its products and technologies. Based upon the
Company's evaluation, it may take no action or it may seek to obtain a license.
There can be no assurance in any given case that a license will be available on
terms the Company considers reasonable, or that litigation will not ensue.
 
                                      F-18
<PAGE>
                                AFFYMETRIX, INC.
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
   (INFORMATION FOR THE SIX MONTHS ENDED JUNE 30, 1996 AND 1997 IS UNAUDITED)
 
NOTE 10--EVENTS SUBSEQUENT TO JUNE 30, 1997 (UNAUDITED)
 
    In July 1997, Affymetrix launched its GeneChip p53 assay for research
applications. The GeneChip p53 assay is the first commercially available DNA
probe array-based product capable of analyzing the full-length coding sequence
of the human p53 tumor suppresser gene, a gene that is mutated in greater than
50% of all human cancers.
 
    In August 1997, Affymetrix entered into an agreement to supply Pfizer Inc.
("Pfizer") with GeneChip instrumentation, software and custom DNA probe arrays.
In exchange for supplying Pfizer with its GeneChip technology, the Company will
receive undisclosed payments and has the potential to earn preclinical, clinical
and commercial milestone payments.
 
    In August 1997, Affymetrix and F. Hoffmann-La Roche Ltd. ("Roche") entered
into a subscription-based supply agreement under which Roche will have broad
access to both custom and standard GeneChip expression arrays and GeneChip
instrumentation for simultaneous monitoring of the expression of thousands of
genes. In addition, Roche will have access to commercially available genotyping
and resequencing applications.
 
    In September 1997, Affymetrix and the Parke-Davis division of the
Warner-Lambert Company ("Parke-Davis") entered into a supply agreement pursuant
to which Parke-Davis will gain access to Affymetrix' GeneChip arrays to monitor
gene expression. Under the terms of the agreement, the Company will supply
Parke-Davis with GeneChip instrumentation, software and custom and standard DNA
probe arrays.
 
    In October 1997, the Company filed a registration statement on Form S-3 with
the Securities and Exchange Commission for an underwritten public offering of up
to 1,725,000 shares of Common Stock. The registration statement has not yet
become effective and there can be no assurance that the offering will be
completed.
 
                                      F-19
<PAGE>
                                  UNDERWRITING
 
    Subject to the terms and conditions of the Underwriting Agreement, the
Company has agreed to sell to each of the U.S. Underwriters named below, and
each of such U.S. Underwriters, for whom Goldman, Sachs & Co., BancAmerica
Robertson Stephens, Credit Suisse First Boston Corporation and NationsBanc
Montgomery Securities, Inc. are acting as representatives, has severally agreed
to purchase from the Company, the respective number of shares of Common Stock
set forth opposite its name below.
 
<TABLE>
<CAPTION>
                                                                                  NUMBER OF
                                                                                  SHARES OF
                                 UNDERWRITER                                    COMMON STOCK
- -----------------------------------------------------------------------------  ---------------
<S>                                                                            <C>
Goldman, Sachs & Co..........................................................
BancAmerica Robertson Stephens...............................................
Credit Suisse First Boston Corporation.......................................
NationsBanc Montgomery Securities, Inc.......................................
 
                                                                               ---------------
    Total....................................................................       1,200,000
                                                                               ---------------
                                                                               ---------------
</TABLE>
 
    The Underwriters may offer up to 100,000 shares of Common Stock to Alejandro
C. Zaffaroni, a founder and director of the Company.
 
    Under the terms and conditions of the Underwriting Agreement, the U.S.
Underwriters are committed to take and pay for all of the shares of Common Stock
offered hereby, if any are taken.
 
    The U.S. Underwriters propose to offer the shares of Common Stock in part
directly to the public at the initial public offering price set forth on the
cover page of this Prospectus and in part to certain securities dealers at such
price less a concession of $    per share. The U.S. Underwriters may allow, and
such dealers may reallow, a concession not in excess of $    per share to
certain brokers and dealers. After the shares of Common Stock are released for
sale to the public, the offering price and other selling terms may from time to
time be varied by the representatives.
 
                                      U-1
<PAGE>
    The Company has entered into an underwriting agreement (the "International
Underwriting Agreement") with the underwriters of the International Offering
(the "International Underwriters") providing for the concurrent offer and sale
of 300,000 shares of Common Stock in an international offering outside the
United States. The offering price and aggregate underwriting discounts and
commissions per share for the two offerings are identical. The closing of the
Offering made hereby is a condition to the closing of the International
Offering, and vice versa. The representatives of the International Underwriters
are Goldman Sachs International, BancAmerica Robertson Stephens, Credit Suisse
First Boston (Europe) Limited and NationsBanc Montgomery Securities, Inc.
 
    Pursuant to an Agreement between the U.S. and International Underwriting
Syndicates (the "Agreement Between") relating to the Offerings, each of the U.S.
Underwriters named herein has agreed that, as a part of the distribution of the
shares offered hereby and subject to certain exceptions, it will offer, sell or
deliver the shares of Common Stock, directly or indirectly, only in the United
States of America (including the States and the District of Columbia), its
territories, its possessions and other areas subject to its jurisdiction (the
"United States") and to U.S. persons, which term shall mean, for purposes of
this paragraph: (a) any individual who is a resident of the United States or (b)
any corporation, partnership or other entity organized in or under the laws of
the United States or any political subdivision thereof and whose office most
directly involved with the purchase is located in the United States. Each of the
International Underwriters has agreed pursuant to the Agreement Between that, as
a part of the distribution of the shares offered as a part of the International
Offering, and subject to certain exceptions, it will (i) not, directly or
indirectly, offer, sell or deliver shares of Common Stock (a) in the United
States or to any U.S. persons or (b) to any person who it believes intends to
reoffer, resell or deliver the shares in the United States or to any U.S.
persons, and (ii) cause any dealer to whom it may sell such shares at any
concession to agree to observe a similar restriction.
 
    Pursuant to the Agreement Between, sales may be made between the U.S.
Underwriters and the International Underwriters of such number of shares of
Common Stock as may be mutually agreed. The price of any shares so sold shall be
the initial public offering price, less an amount not greater than the selling
concession.
 
    The Company has granted the U.S. Underwriters an option exercisable for 30
days after the date of this Prospectus to purchase up to an aggregate of 180,000
additional shares of Common Stock solely to cover over-allotments, if any. If
the U.S. Underwriters exercise their over-allotment option, the U.S.
Underwriters have severally agreed, subject to certain conditions, to purchase
approximately the same percentage thereof that the number of shares to be
purchased by each of them, as shown in the foregoing table, bears to the
1,200,000 shares of Common Stock offered. The Company has granted the
International Underwriters a similar option to purchase up to an aggregate of
45,000 additional shares of Common Stock.
 
    The Underwriters have requested that the Company, Glaxo and each of the
officers and directors of the Company agree that, during the period beginning
from the date of this Prospectus and continuing to and including the date 90
days after the date of the Prospectus, they will not offer, sell, contract to
sell or otherwise dispose of any securities of the Company (other than pursuant
to employee stock option plans existing, or on the conversion or exchange of
convertible or exchangeable securities outstanding, on the date of this
Prospectus) which are substantially similar to the shares of the Common Stock or
which are convertible into or exchangeable for securities which are
substantially similar to the shares of Common Stock without the prior written
consent of the representatives, except for the shares of Common Stock offered in
connection with the Offerings.
 
    In connection with the Offerings, the Underwriters may purchase and sell the
shares of Common Stock in the open market. These transactions may include
over-allotment and stabilizing transactions, "passive" market making (see below)
and purchases to cover syndicate short positions created in connection with the
Offerings. Stabilizing transactions consist of certain bids or purchases for the
 
                                      U-2
<PAGE>
purpose of preventing or retarding a decline in the market price of the Common
Stock; and syndicate
short positions involve the sale by the Underwriters of a greater number of
shares of Common Stock than they are required to purchase from the Company in
the Offerings. The Underwriters also may impose a penalty bid, whereby selling
concessions allowed to syndicate members or other broker-dealers in respect of
the shares of Common Stock sold in the Offerings for their account may be
reclaimed by the syndicate if such shares of Common Stock are repurchased by the
syndicate in stabilizing or covering transactions. These activities may
stabilize, maintain or otherwise affect the market price of the Common Stock,
which may be higher than the price that might otherwise prevail in the open
market; and these activities, if commenced, may be discontinued at any time.
These transactions may be effected on the Nasdaq National Market, in the
over-the-counter market or otherwise.
 
    As permitted by Rule 103 under the Exchange Act, certain Underwriters (and
selling group members, if any) that are market makers ("passive market makers")
in the shares of Common Stock may make bids for or purchases of the shares of
Common Stock in the Nasdaq National Market until such time, if any, when a
stabilizing bid for the shares of Common Stock has been made. Rule 103 generally
provides that (1) a passive market maker's net daily purchases of the Common
Stock may not exceed 30% of its average daily trading volume in the Common Stock
for the two full consecutive calendar months (or any 60 consecutive days ending
within the 10 days) immediately preceding the filing date of the registration
statement of which this Prospectus forms a part, (2) a passive market maker may
not effect transactions or display bids for the shares of Common Stock at a
price that exceeds the highest independent bid for the shares of Common Stock by
persons who are not passive market makers and (3) bids made by passive market
makers must be identified as such.
 
    The shares of Common Stock are quoted on the Nasdaq National Market under
the symbol "AFFX".
 
    The Company has agreed to indemnify the several Underwriters against certain
liabilities, including liabilities under the Securities Act of 1933, as amended.
 
    This Prospectus may be used by underwriters and dealers in connection with
offers and sales of the shares of Common Stock, including shares initially sold
in the International Offering, to persons located in the United States.
 
                                      U-3
<PAGE>
                AFFYMETRIX GENECHIP-REGISTERED TRADEMARK- SYSTEM
 
PHOTOLITHOGRAPHY
 
    Affymetrix manufactures wafers of GeneChip-Registered Trademark- probe
arrays using a high resolution photolithographic fabrication process adapted
from the semiconductor industry. A wafer is shown being exposed to ultraviolet
light through a lithographic mask.
 
    [PHOTO OF THE PHOTOLITHOGRAPHIC INSTRUMENTATION USED TO SYNTHESIZE GENECHIP
                                 PROBE ARRAYS.]
 
WAFER-SCALE PRODUCTION
 
    Affymetrix achieves manufacturing efficiencies by simultaneously
synthesizing many probe arrays on a single wafer. A wafer, diced into individual
probe arrays, is shown being packaged into cartridges.
 
    [PICTURE OF ROBOTICS USED TO PACKAGE GENECHIP PROBE ARRAYS INTO CARTRIDGES.]
 
INTEGRATED GENECHIP-REGISTERED TRADEMARK- SYSTEM
 
    The GeneChip Fluidics Station controls hybridization of the test sample to
the probe array. The GeneChip Scanner quantitatively detects hybridization of a
test sample to the probe array. GeneChip software analyzes and manages genetic
information from the scanner.
 
     [PHOTO OF THE GENECHIP SYSTEM INCLUDING THE SCANNER, FLUIDICS STATION AND
                                 WORKSTATION.]
<PAGE>
- ----------------------------------------------------
                            ----------------------------------------------------
- ----------------------------------------------------
                            ----------------------------------------------------
 
    NO PERSON HAS BEEN AUTHORIZED TO GIVE ANY INFORMATION OR TO MAKE ANY
REPRESENTATIONS OTHER THAN THOSE CONTAINED IN THIS PROSPECTUS, AND, IF GIVEN OR
MADE, SUCH INFORMATION OR REPRESENTATIONS MUST NOT BE RELIED UPON AS HAVING BEEN
AUTHORIZED. THIS PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL OR THE
SOLICITATION OF AN OFFER TO BUY ANY SECURITIES OTHER THAN THE SECURITIES TO
WHICH IT RELATES OR AN OFFER TO SELL OR THE SOLICITATION OF AN OFFER TO BUY SUCH
SECURITIES IN ANY CIRCUMSTANCES IN WHICH SUCH OFFER OR SOLICITATION IS UNLAWFUL.
NEITHER THE DELIVERY OF THIS PROSPECTUS NOR ANY SALE MADE HEREUNDER SHALL, UNDER
ANY CIRCUMSTANCES, CREATE ANY IMPLICATION THAT THERE HAS BEEN NO CHANGE IN THE
AFFAIRS OF THE COMPANY SINCE THE DATE HEREOF OR THAT THE INFORMATION CONTAINED
HEREIN IS CORRECT AS OF ANY TIME SUBSEQUENT TO ITS DATE.
 
                              --------------------
 
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                                            PAGE
                                                                            ----
<S>                                                                         <C>
Available Information.....................................................    3
Incorporation of Certain Documents by Reference...........................    3
Prospectus Summary........................................................    4
Risk Factors..............................................................    7
Use of Proceeds...........................................................   22
Price Range of Common Stock...............................................   23
Dividend Policy...........................................................   23
Capitalization............................................................   24
Dilution..................................................................   25
Selected Financial Data...................................................   26
Management's Discussion and Analysis of Financial Condition and Results of
  Operations..............................................................   27
Business..................................................................   31
Management................................................................   53
Validity of Common Stock..................................................   56
Experts...................................................................   56
Index to Financial Statements.............................................  F-1
Underwriting..............................................................  U-1
</TABLE>
 
                                1,500,000 SHARES
 
                                AFFYMETRIX, INC.
 
                                  COMMON STOCK
                                 (NO PAR VALUE)
 
                             ---------------------
 
                                     [LOGO]
                             ---------------------
 
                              GOLDMAN, SACHS & CO.
 
                         BANCAMERICA ROBERTSON STEPHENS
 
                           CREDIT SUISSE FIRST BOSTON
 
                    NATIONSBANC MONTGOMERY SECURITIES, INC.
 
                      REPRESENTATIVES OF THE UNDERWRITERS
 
- ----------------------------------------------------
                            ----------------------------------------------------
- ----------------------------------------------------
                            ----------------------------------------------------
<PAGE>
                                    PART II
                     INFORMATION NOT REQUIRED IN PROSPECTUS
 
ITEM 14.  OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION
 
    The following table sets forth the costs and expenses, other than
underwriting discounts and commissions, payable by the registrant in connection
with the sale and distribution of the Common Shares being registered. All of the
amounts shown are estimates except for the Securities and Exchange Commission
Registration Fee, the NASD filing fee and the Nasdaq National Market Application
Fee.
 
<TABLE>
<S>                                                                <C>
Securities and Exchange Commission Registration Fee..............  $  22,347
NASD Filing Fee..................................................      7,875
Nasdaq National Market Application Fee...........................     17,500
Blue Sky Qualification Fees and Expenses.........................      5,000
Accounting Fees..................................................     50,000
Legal Fees and Disbursements (including Blue Sky)................    150,000
Transfer Agent and Registrar Fees................................      5,000
Printing and Engraving...........................................    100,000
Travel...........................................................    100,000
Miscellaneous....................................................     42,278
                                                                   ---------
  Total:.........................................................  $ 500,000
                                                                   ---------
                                                                   ---------
</TABLE>
 
ITEM 15.  INDEMNIFICATION OF OFFICERS AND DIRECTORS
 
    Pursuant to Section 204(a) and 317 of the California Corporations Code, as
amended, the registrant has included in its articles of incorporation and
by-laws provisions regarding the indemnification of officers and directors of
the registrant. Article Four of registrant's Restated Articles of Incorporation,
as amended, provides as follows:
 
    "The liability of the directors of this corporation for monetary damages
shall be eliminated to the fullest extent permissible under California law. This
corporation is also authorized, to the fullest extent permissible under
California law, to indemnify its agents (as defined in Section 317 of the
California Corporations Code), whether by by-law, agreement or otherwise, for
breach of duty to this corporation and its shareholders in excess of the
indemnification expressly permitted by Section 317 and to advance defense
expenses to its agents in connection with such matters as they are incurred,
subject to the limits on such excess indemnification set forth in Section 204 of
the California Corporations Code. If, after the effective date of this Article,
California law is amended in a manner which permits a corporation to limit the
monetary or other liability of its directors or to authorize indemnification of,
or advancement of such defense expenses to, its directors or other persons, in
any such case to a greater extent than is permitted on such effective date, the
references in this Article to "California law" shall to that extent be deemed to
refer to California law as so amended."
 
    Section 29 of the registrant's By-Laws, as amended, provides as follows:
 
  "29. INDEMNIFICATION OF DIRECTORS AND OFFICERS.
 
    (a) INDEMNIFICATION.  To the fullest extent permissible under California
law, the corporation shall indemnify its directors and officers against all
expenses, judgement, fines, settlements and other amounts actually and
reasonably incurred by them in connection with any proceeding, including an
action by or in the right of the corporation, by reason of the fact that such
person is or was a director or officer of the corporation, or is or was serving
at the request of the corporation as a director, officer, trustee, employee or
agent of another corporation, or of a partnership, joint venture, trust or other
enterprise (including service with respect to employee benefit plans). To the
fullest extent permissible
 
                                      II-1
<PAGE>
under California law, expenses incurred by a director or officer seeking
indemnification under this By-law in defending any proceeding shall be advanced
by the corporation as they are incurred upon receipt by the corporation of an
undertaking by or on behalf of the director or officer to repay such amount if
it shall ultimately be determined that the director or officer is not entitled
to be indemnified by the corporation for those expenses. If, after the effective
date of this By-law, California law is amended in a manner which permits the
corporation to authorize indemnification of or advancement of expenses to its
directors or officers, in any such case to a greater extent than is permitted on
such effective date, the references in this By-law to "California law" shall to
that extent be deemed to refer to California law as so amended. The rights
granted by this By-law are contractual in nature and, as such, may not be
altered with respect to any present or former director or officer without the
written consent of that person.
 
    (b) PROCEDURE.  Upon written request to the Board of Directors by a person
seeking indemnification under this By-law, the Board shall promptly determine in
accordance with Section 317(e) of the California Corporations Code whether the
applicable standard of conduct has been met and, if so, the Board shall
authorize indemnification. If the Board cannot authorize indemnification because
the number of directors who are parties to the proceeding with respect to which
indemnification is sought prevents the formation of a quorum of directors who
are not parties to the proceeding, then, upon written request by the person
seeking indemnification, independent legal counsel (by means of a written
opinion obtained at the corporation's expense) or the corporation's shareholders
shall determine whether the applicable standard of conduct has been met and, if
so, shall authorize indemnification.
 
    (c) DEFINITIONS.  The term "proceeding" means any threatened, pending or
completed action or proceeding, whether civil, criminal, administrative or
investigative. The term "expenses" includes, without limitation, attorney's fees
and any expenses of establishing a right to indemnification."
 
ITEM 16.  EXHIBITS
 
        (a) Exhibit
 
<TABLE>
<C>          <S>
       *1.1  Form of Underwriting Agreement
       *5.1  Opinion of Heller Ehrman White & McAuliffe
      +10.1  Supply Agreement among F. Hoffmann-La Roche Ltd., Hoffmann-La Roche
              Inc., Syntex (U.S.A.) Inc. and Affymetrix, Inc. effective as of August
              15, 1997.
       10.2  Fourth Amendment to the Lease between Sobrato Interests and Affymetrix,
              Inc. dated effective May 31, 1996
       10.3  Lease between Sobrato Interests and Affymetrix, Inc. dated effective
              May 31, 1996
      *23.1  Consent of Heller Ehrman White & McAuliffe (included in Exhibit 5.1)
       23.2  Consent of Townsend Townsend and Crew LLP
       23.3  Consent of Ernst & Young LLP, Independent Auditors
       24    Power of Attorney (See Pages II-4)
</TABLE>
 
- --------------
 
*   To be filed by amendment.
 
+   Confidential treatment requested.
 
ITEM 17.  UNDERTAKINGS
 
    A.  The undersigned Company hereby undertakes:
 
        (1) To file, during any period in which offers or sales are being made,
    a post-effective amendment to this registration statement;
 
                                      II-2
<PAGE>
           (i)  To include any prospectus required by section 10(a)(3) of the
               Securities Act of 1933;
 
           (ii) To reflect in the prospectus any facts or events arising after
               the effective date of the Registration Statement (or the most
               recent post-effective amendment thereof) which, individually or
               in the aggregate, represent a fundamental change in the
               information set forth in the Registration Statement;
 
           (iii) To include any material information with respect to the plan of
               distribution not previously disclosed in the Registration
               Statement or any material change to such information in the
               Registration Statement;
 
    Provided, however, that paragraphs (i) and (ii) shall not apply if the
information required to be included in a post-effective amendment by those
paragraphs is contained in periodic reports filed by the registrant pursuant to
section 13 or section 15(d) of the Securities Exchange Act of 1934 that are
incorporated by reference in the Registration Statement.
 
        (1) That, for the purpose of determining any liability under the
    Securities Act of 1933, each such post-effective amendment shall be deemed
    to be a new Registration Statement relating to the securities offered
    therein, and the offering of such securities at that time shall be deemed to
    be the initial bona fide offering thereof.
 
        (2) To remove from registration by means of a post-effective amendment
    any of the securities being registered which remain unsold at the
    termination of the offering.
 
        (3) For purposes of determining any liability under the Securities Act
    of 1933, the information omitted from the form of prospectus filed as part
    of this registration statement in reliance upon Rule 430A and contained in a
    form of prospectus filed by the registrant pursuant to Rule 424(b)(1) or (4)
    or 497(h) under the Securities Act shall be deemed to be part of this
    registration statement as of the time it was declared effective.
 
        (4) For the purpose of determining any liability under the Securities
    Act of 1933, each post-effective amendment that contains a form of
    prospectus shall be deemed to be a new registration statement relating to
    the securities offered therein, and the offering of such securities at that
    time shall be deemed to be the initial bona fide offering thereof.
 
    C.  Insofar as indemnification for liabilities arising under the Securities
Act of 1933 may be permitted to directors, officers and controlling persons of
the Registrant pursuant to the foregoing provisions, or otherwise, the
Registrant has been advised that in the opinion of the Securities and Exchange
Commission, such indemnification is against public policy as expressed in the
Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
Registrant of expenses incurred or paid by a director, officer or controlling
person of the Registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the Registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Act and will
be governed by the final adjudication of such issue.
 
                                      II-3
<PAGE>
                                   SIGNATURES
 
    Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-3 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized in the City of Santa Clara, State of California, on the 17th day of
October 1997.
 
<TABLE>
<S>                             <C>  <C>
                                AFFYMETRIX, INC.
 
                                By:            /s/ EDWARD M. HURWITZ
                                     -----------------------------------------
                                                 Edward M. Hurwitz
                                              CHIEF FINANCIAL OFFICER
</TABLE>
 
                               POWER OF ATTORNEY
 
    Each person whose signature appears below constitutes and appoints John D.
Diekman, Stephen P.A. Fodor and Edward M. Hurwitz his true and lawful
attorneys-in-fact and agents, each acting alone, with full power of substitution
and resubstitution, for him and in his name, place and stead, in any and all
capacities, to sign any or all amendments (including post-effective amendments)
to the Registration Statement, and to sign any registration statement for the
same offering covered by this Registration Statement that is to be effective
upon filing pursuant to Rule 462(b) under the Securities Act of 1933, as
amended, and all post-effective amendments thereto, and to file the same, with
all exhibits thereto, and all documents in connection therewith, with the
Securities and Exchange Commission, granting unto said attorneys-in-fact and
agents, full power and authority to do and perform each and every act and thing
requisite and necessary to be done in and about the premises, as fully to all
intents and purposes as he might or could do in person, hereby ratifying and
confirming all that said attorneys-in-fact and agents, each acting alone, or his
substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
 
    Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement on Form S-3 has been signed below by the following
persons in the capacities and on the dates indicated.
 
                                Director, President and
    /s/ STEPHEN P.A. FODOR        Chief Executive Officer
- ------------------------------    (Principal Executive       October 17, 1997
  Stephen P.A. Fodor, Ph.D.       Officer)
 
     /s/ JOHN D. DIEKMAN
- ------------------------------  Chairman of the Board        October 17, 1997
    John D. Diekman, Ph.D.
 
        /s/ PAUL BERG
- ------------------------------  Director                     October 17, 1997
       Paul Berg, Ph.D.
 
- ------------------------------  Director                     October   , 1997
       Douglas M. Hurt
 
                                      II-4
<PAGE>
<TABLE>
<C>                             <S>                         <C>
- ------------------------------  Director                     October   , 1997
    Vernon R. Loucks, Jr.
 
- ------------------------------  Director                     October   , 1997
     Barry C. Ross, Ph.D.
 
     /s/ DAVID B. SINGER
- ------------------------------  Director                     October 17, 1997
       David B. Singer
 
      /s/ LUBERT STRYER
- ------------------------------  Director                     October 17, 1997
     Lubert Stryer, M.D.
 
- ------------------------------  Director                     October   , 1997
        John A. Young
 
  /s/ ALEJANDRO C. ZAFFARONI
- ------------------------------  Director                     October 17, 1997
Alejandro C. Zaffaroni, Ph.D.
 
    /s/ EDWARD M. HURWITZ       Chief Financial Officer
- ------------------------------    (Principal Financial and   October 17, 1997
      Edward M. Hurwitz           Accounting Officer)
</TABLE>
 
                                      II-5
<PAGE>
                               INDEX TO EXHIBITS
 
<TABLE>
<CAPTION>
                                                                                 PAGES
                                                                                 ------
<C>    <S>                                                                       <C>
 *1.1  Form of Underwriting Agreement
 
 *5.1  Opinion of Heller Ehrman White & McAuliffe
 
+10.1  Supply Agreement among F. Hoffmann-La Roche Ltd., Hoffmann-La Roche Inc.,
        Syntex (U.S.A.) Inc. and Affymetrix, Inc. effective as of August 15,
        1997.
 
 10.2  Fourth Amendment to the Lease between Sobrato Interests and Affymetrix,
        Inc. dated effective May 31, 1996
 
 10.3  Lease between Sobrato Interests and Affymetrix, Inc. dated effective May
        31, 1996
 
*23.1  Consent of Heller Ehrman White & McAuliffe (included in Exhibit 5.1)
 
 23.2  Consent of Townsend and Townsend and Crew
 
 23.3  Consent of Ernst & Young LLP, Independent Auditors
 
 24    Power of Attorney (See Pages II-4)
</TABLE>
 
- --------------
 
 *  To be filed by amendment.
 
 +  Confidential treatment requested.
 
                                      II-6

<PAGE>



                                   SUPPLY AGREEMENT

                             F. Hoffmann-La Roche Ltd,
                              Hoffmann-La Roche Inc.,
                                 Syntex (U.S.A.) Inc.
                                         and
                                   Affymetrix, Inc.


            The symbol "**" is used throughout this exhibit to indicate
            that a portion of the exhibit has been omitted and filed 
            separately with the commission.

<PAGE>

CONTENTS

1   INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3

2   DEFINITIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3

3   PROBE ARRAY AND INSTRUMENT SUPPLY. . . . . . . . . . . . . . . . . . .  6

4   EXCLUSIVITY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5   COMPENSATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

6   INTELLECTUAL PROPERTY. . . . . . . . . . . . . . . . . . . . . . . . . 14

7   PROJECT COORDINATION . . . . . . . . . . . . . . . . . . . . . . . . . 15

8   CONFIDENTIALITY. . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

9   WARRANTY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

10  INDEMNITY  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

11  TERM AND TERMINATION . . . . . . . . . . . . . . . . . . . . . . . . . 18

12  MISCELLANEOUS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

EXHIBIT A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

                                          2
<PAGE>

This supply agreement ("Agreement") is effective  as of August  15,  1997
("Effective Date") between Affymetrix, Inc. ("AFFX") a California corporation
having its principal place of business at 3380 Central Expressway, Santa Clara,
California 95051, and F. Hoffmann-La Roche Ltd,  a Swiss corporation having a
principal place of business at Grenzacherstrasse 127, 4070 Basel, Switzerland,
and Hoffmann-La Roche Inc., a New Jersey Corporation having its principal place
of business at 340 Kingsland Street, Nutley, New Jersey 07110, USA, and
Syntex (U.S.A.) Inc., a Delaware corporation having its principal place of
business at 3401 Hillview Avenue, Palo Alto, California, 94304, acting through
its Roche Bioscience division (all collectively referred to as "Roche").

1         INTRODUCTION

1.1       AFFX has research, development, and manufacturing capabilities and
          facilities, and has developed certain rights relevant to DNA probe
          array based technology.

1.2       Roche has research and development capabilities, and facilities to
          conduct research and development activities in the area of
          pharmaceutical research.

1.3       AFFX and Roche desire to enter into an agreement whereby AFFX will
          supply Roche with DNA probe arrays for use in Roche's research and
          development activities.

In consideration of the mutual covenants and promises contained in this
Agreement, AFFX and Roche agree as follows:

2         DEFINITIONS

2.1       "Affiliate" shall mean any corporation, company, partnership, joint
          venture and/or firm which is controlled by or controls a Party or is
          under common control with a Party, but only for so long as such
          Affiliate remains an Affiliate of a Party, and only if such Affiliate
          is bound by the terms of this Agreement.  For purposes of this
          Section, "control" shall mean, in the case of corporations (or
          equivalents of corporations), direct or indirect ownership of at least
          50% of the stock having the right to vote for directors of such
          corporation or, in the case of partnerships, at least 50% of the
          ownership interest in such partnership. Genentech, Inc., South San
          Francisco, California, USA, shall not be considered an Affiliate of
          Roche unless Roche elects in writing at its sole option to have
          Genentech, Inc. be an Affiliate of Roche.


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2.2       "Chip Improvement Inventions" shall mean all inventions for which
          patent applications are filed that are conceived or first reduced to
          practice by an employee or contractor of a Party during performance of
          a Chip Project or using the Probe Arrays supplied hereunder, and
          specifically relating to probe array manufacturing techniques, probe
          array layouts, probe array packaging techniques, probe array assay
          techniques (but only insofar as such assay techniques relate to
          processes after nucleic acid extraction and are directly related to
          arrays of nucleic acid probes), and probe array software analysis
          techniques relating to the extraction of data from probe arrays and
          storing such data in a computer file, but not including software
          analysis techniques for later processing of such data.  Chip
          Improvement Inventions shall not include, for example, expression data
          or discoveries resulting therefrom, targets identified through the use
          of the Probe Arrays, or correlations between genetic sequences and
          function.

2.3       "Chip Project" shall refer to the design and manufacture of a Lot of
          Probe Arrays for a particular Target Sequence, as specified by Roche
          pursuant to this Agreement.

2.4       "Collaborator" shall mean a third party involved in a Roche
          Collaboration, but only to the extent of such Roche Collaboration.

2.5       "Committee" shall mean the individuals designated by Roche and AFFX to
          serve on a coordinating committee as outlined in Section 7.

2.6       "Confidential Information" shall mean all information and materials,
          patentable or otherwise, of a Party disclosed by or on behalf of such
          Party to the other Party and which derive value to a Party from not
          being generally known, including, but not limited to DNA sequences,
          vectors, cells, substances, formulations, techniques, methodology,
          equipment, data, reports, know-how, preclinical and clinical trials
          and the results thereof, sources of supply, patent positioning, and
          business plans, including any negative developments.

2.7       "Fabrication Verification Criteria" shall mean the criteria set forth
          in Exhibit A.

2.8       "Lot" shall refer to [**] Probe Arrays directed to a particular 
          Target Sequence.  AFFX shall have a right, upon seven (7) months 
          written notice to Roche, to vary the size of a Lot upwards or 
          downwards, provided that the size of a Lot may not be increased 
          above [**] Probe Arrays without the prior written consent of Roche. 
          Standard Configuration Expression Probe Arrays and Other Standard 
          Probe Arrays may be purchased in their standard minimum quantities.

2.9       "Party" shall mean AFFX or Roche.  "Parties" shall mean AFFX and
          Roche.


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2.10      "Probe Arrays" shall mean a solid support having an array of
          oligonucleotides with known location and sequence fabricated pursuant
          to this Agreement.

2.11      "Resupply Term" shall mean the period of time beginning at the end of
          the Term of this Agreement, and extending up to 3  years from the end
          of the Term of this Agreement.

2.12      "Roche's Area Of Interest" shall mean the use of Probe Arrays [**]. 
          For purposes of clarity, [**] within the scope of this Agreement.  
          Roche's Area of Interest shall include Roche Collaborations [**].  
          Roche's Area Of Interest [**].

2.13      "Roche Collaboration(s)" shall mean a bona fide scientific
          collaboration between Roche or any of its Affiliates and a third party
          under a written contract and research plan in a specified area, in
          which a) such third party receives the biological materials and/or
          proprietary information of Roche and/or its Affiliates, or in which
          Roche and/or its Affiliates obtains the biological materials and/or
          proprietary information of the third party, and b) Roche obtains
          significant proprietary rights if significant intellectual property is
          generated in the collaboration, and c) the collaboration is within
          Roche's normal (as of the Effective Date) business model  (For
          purposes of this Agreement, "Roche's normal business model" shall
          include, for example, pharmaceutical and diagnostics research,
          development, and marketing, but does not include nucleic acid
          hybridization services or database distribution businesses.),  and d)
          in which Roche and its collaborator provide significant scientific
          input to the collaboration in addition to data obtained from the Probe

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          Arrays where "significant scientific input" includes, for example,
          material input to experimental design, material contributions to
          experimental execution, and/or material data analysis activities, and
          e) in which, at the time the gene expression information is generated,
          such gene expression information is generated primarily for use by
          Roche for the purpose of researching, developing and/or
          commercializing particular molecules, classes of molecules, or
          therapeutic areas.  Roche will not enter into arrangements with third
          parties whereby such third party is, in effect, given broad access to
          i) the Probe Arrays or, ii) data resulting from use of the Probe
          Arrays. By way of example,  Roche Collaborations shall not include
          business relationships based, in significant part, on a contract in
          which Roche provides contract services for a third party involving use
          of the Probe Arrays on a fee-for-service or similar basis. Roche
          Collaborations shall not provide for the access of the Probe Arrays to
          a company that engages in a bona fide business in the sale of probe
          array based assays or services.  A Roche Collaboration shall include
          work with academic investigators provided that:

2.13.1    [**]

2.13.2    [**]

2.13.3    [**]

2.14      "Standard Configuration Expression Probe Arrays" shall mean Probe
          Arrays that are generally made available to third parties based on a
          single mask set design for use in expression monitoring experiments
          which are sold at standard catalog prices or which are broadly
          available to any third party that is willing to pay to AFFX fixed fees
          set by AFFX. "Other Standard Configuration Probe Arrays" shall include
          genotyping probe arrays and


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          resequencing probe arrays then made available by AFFX generally to
          third parties in its standard price list.

2.15      "System(s)" shall mean fluidics station(s), work station(s), probe
          array reader(s), and associated software, such software  licensed to
          Roche, and such fluidics station(s) and probe array reader(s) sold to
          Roche.

2.16      "Target Sequence" shall mean a set of sequences specified by Roche to
          AFFX for which Roche desires to have AFFX perform a Chip Project.

2.17      "Term" shall mean the period beginning on the Effective Date and
          ending on December 31, 2000.  The Term may be extended pursuant to
          Sections 5.2 or 5.6 below.

3         PROBE ARRAY AND INSTRUMENT SUPPLY

3.1       During the Term, Roche may identify Target Sequences for Chip 
          Projects.  AFFX will be obligated to produce and supply to Roche 
          Probe Arrays for all Target Sequences identified to AFFX before the 
          end of the Term for up to [**] thereafter.  AFFX will use 
          reasonable efforts to perform Chip Projects for greater numbers of 
          Target Sequences if Roche indicates it will use such greater chip 
          design capacity and the limits in this Section will be modified 
          accordingly provided that in no event will the limits above be 
          increased by more than [**]. In no event will AFFX be required to 
          supply Probe Arrays that have larger numbers of probes or longer 
          probes than those normally furnished commercially to third parties 
          for similar uses.  In addition, upon reasonable advance notice to 
          AFFX that Roche reasonably expects to use greater capacity for 
          Probe Array design, AFFX will reasonably expand its Probe Array 
          design capabilities to accommodate such increased demand by Roche. 
          Prices of Probe Arrays reflected in Section 5 reflect such Probe 
          Array specifications for arrays up to [**].  AFFX will provide 
          Roche with Probe Arrays with greater [**] and/or with other 
          commercially available improvements to AFFX' current expression 
          probe array technology; provided that in the event that arrays are 
          to be provided during the course of this Agreement with more than 
          [**] or with other commercially available improvements to AFFX' 
          current expression probe array technology, AFFX will provide Roche 
          with reasonable quotes for such Probe Arrays, provided that such 
          pricing must be reasonably reflective of the prices AFFX charges to 
          other entities for such Probe Arrays


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          under similar commercial terms, if such probe arrays are sold to third
          parties, and if such Probe Arrays are not sold to third parties, such
          pricing must be reflective of the prices charged to third parties of
          those chips most similar in nature to those to be provided to Roche.

3.2       Roche will identify the Target Sequence for a Custom Chip Project 
          to AFFX by delivering to AFFX: 1) a diskette identifying the Target 
          Sequence in "Intelligenetics" or "GenBank" format, and 2) an 
          identification of [**] and 4) a good faith estimate of the number 
          of Lots of Probe Arrays needed by Roche for the Target Sequence and 
          the expected timing for production of such Lots as specified in 
          Section 3.4, and 5) an initial firm order for at least one Lot of 
          Probe Arrays directed to the Target Sequence, and 6) the shipping 
          location of the Probe Arrays.  Probe Arrays may be ordered only in 
          full Lots (it being understood that Standard Configuration 
          Expression Probe Arrays and Other Standard Probe Arrays may be 
          purchased in their standard lot size).  Roche may request that the 
          Probe Arrays meet specifications suggested by Roche and not 
          provided for herein, in which case AFFX will respond in good faith 
          as to whether such additional specifications can reasonably be met 
          and, if applicable, any  price increase to meet such additional or 
          modified specifications.

3.3       AFFX will promptly confirm receipt of the Target Sequence within 
          three (3) business days.  If  the information received by AFFX does 
          not include the information required in paragraph 3.2 above,  AFFX 
          will advise Roche of any additional needed information within five 
          (5) business days of receipt of a Target Sequence.  Upon AFFX 
          confirming receipt of complete Target Sequence information, AFFX 
          will proceed to design, lay out,  produce masks,  and manufacture 
          Probe Arrays for the Target Sequence  according to the following 
          schedule:  a) for resupply of previously ordered Probe Arrays, AFFX 
          will deliver such Probe Arrays within [**] of receipt of a firm 
          order, and  b) for initial orders, AFFX will deliver such Probe 
          Arrays within [**] of receipt of the complete information specified 
          in Section 3.2.  In no event will AFFX be obligated to provide more 
          than [**] thereafter.  AFFX will make reasonable efforts to supply 
          Probe Arrays ordered by Roche in quantities greater than specified 
          above.   In addition, upon reasonable advance notice to AFFX that 
          Roche will use greater capacity for Probe Array manufacturing, AFFX 
          will reasonably


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          expand its Probe Array manufacturing capabilities to accommodate such
          increased demand by Roche and the limits in this Section will be
          modified accordingly provided that in no event will the limits above
          be increased by more than [**].  It is understood that the Roche
          forecasts and supply limitations  above will not be impacted by the
          test probe arrays provided at no cost in Section 3.4 or 3.10.  Roche
          will include forecasts for test probe arrays to be purchased by Roche,
          but the supply limitations above will not be impacted by such
          purchased test probe arrays.

3.3.1     Before the end of the Resupply Term, Roche may order additional full
          Lots of Probe Arrays for a particular Custom Chip Project.  The
          Parties agree that this paragraph shall not obligate AFFX to store
          masks beyond the Resupply Term, provided that prior to destroying any
          masks, AFFX shall notify Roche in writing and all such masks for Roche
          Chip Projects will, upon request of Roche, be given to Roche. No
          license is conveyed to Roche by way of the transfer of masks; such
          masks are transferred only for storage purposes.

3.4       On the first day of each month during the term of this Agreement, 
          Roche will provide a reasonable, good faith forecast of Probe 
          Arrays to be designed, supplied, and resupplied by AFFX during the 
          following [**] period.  The forecast will be provided according to 
          a mechanism and on forms to be agreed upon in good faith by the 
          Parties. The [**] of such forecast shall constitute a firm 
          commitment for initial orders and resupply of the Probe Arrays 
          specified in each such [**] forecast, and AFFX will be provided 
          with Target Sequences for new Chip Projects, if any, for such [**] 
          of such forecast. The [**] of such forecast shall constitute a firm 
          order for the quantities of Probe Arrays specified therein, but not 
          the particular designs, and Roche need not specify the particular 
          designs to be ordered.  The [**] of such forecast shall constitute 
          a firm order for at least [**] of the quantities of Probe Arrays 
          specified in such forecast, but not the particular designs, and 
          Roche need not specify the particular designs to be ordered.  In 
          the event that actual orders are less than such firm orders, Roche 
          shall compensate AFFX as though such firm orders were met.  The [**]
          of forecast shall be for planning purposes only, but will be made 
          in good faith by Roche. AFFX will make good faith efforts to supply 
          and design Probe Arrays in quantities greater than have been 
          previously forecast in the [**] by Roche, but will not be obligated 
          to do so, and Roche will be obligated to reimburse AFFX for any 
          non-cancelable orders of equipment which are reasonably incurred by 
          AFFX in scaling its production facilities to meet the forecasts of 
          Roche.  In no event will Roche be required to pay such 
          non-cancelable costs unless AFFX notifies Roche of the need for 
          such increased production capacity, and provides Roche with 
          reasonable estimates of the magnitude of such non-cancelable costs. 
          If requested by one of the Parties, the Committee will negotiate


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          in good faith to modify the above forecasting procedure to reasonably
          accommodate the business needs of the other Party.  During each
          calendar month in which Roche purchases at least one (1) Lot of Probe
          Arrays, AFFX will provide to Roche a lot of AFFX' standard test probe
          arrays (in a lot size equal to the lot size of custom Probe Arrays)
          for purposes of and only for purposes of sample quality control and
          training at Roche at no additional charge.  Additional standard test
          probe arrays may be acquired for [**] each at Roche's option.

3.5       Probe Arrays will be packed in AFFX' standard shipping packages to the
          address specified by Roche.  Deliveries will be F.O.B. AFFX' facility.
          AFFX will ship via a carrier selected by Roche or, if none is
          specified by Roche, AFFX will select the carrier.  Title and risk of
          loss of damage for deliveries will pass to Roche upon AFFX' actual
          delivery of the Probe Arrays to the carrier for shipment to Roche.
          Roche will pay all shipping costs.  Roche will advise AFFX if
          insurance is desired on any shipments of Probe Arrays, and will
          reimburse AFFX for all such insurance charges.

3.6       Roche may not 1) transfer the Probe Arrays provided by AFFX pursuant
          to this Agreement except as to Collaborators in Roche's Area of
          Interest,  or 2) transfer data generated therewith to any third party,
          other than to Collaborators in Roche's Area of Interest or Affiliates,
          or 3) provide services to any third party, other than to Affiliates,
          using the Probe Arrays provided by AFFX pursuant to the Agreement, or
          4) allow any third party, other than Affiliates to use the Probe
          Arrays provided by AFFX under this Agreement, except as to
          Collaborators in Roche's Area of Interest, or 5) use the Probe Arrays
          delivered hereunder outside of Roche's Area of Interest, or 6) reuse
          the Probe Arrays, or 7) use such Probe Arrays in diagnostic or other
          settings requiring FDA or other regulatory agency approval unless
          Roche obtains such approval and such Probe Arrays are to be used in a
          clinical trial.  Roche will allow AFFX reasonable, periodic (but not
          more than quarterly)  access to the Systems to ensure compliance with
          the prohibition against reuse.

3.7       Roche and AFFX expect that during the Term they will periodically
          cooperate in the experimental manufacture of designs of Probe Arrays
          that are more complex than those provided for herein or which might
          otherwise be expected to have experimental features.  Such Probe
          Arrays will be provided upon the concurrence of both Parties but will
          not be required to meet the Fabrication Verification Criteria.

3.8       During the Term and the Resupply Term of the Agreement, Roche may
          purchase Standard Configuration Expression Probe Arrays and Other
          Standard Probe Arrays within the volume forecasts set forth herein and
          at the prices provided herein (it being understood that the design
          fees will not be applicable to such Standard Configuration Expression
          Probe


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          Arrays or Other Standard Probe Arrays).  [**]

3.9       [**] Systems will be provided to Roche and installed at no 
          additional cost during the first year from the Effective Date.  [**]
          Such Systems will be delivered according to a phase in program to 
          be mutually agreed upon by the Parties.  During the Term and the 
          Resupply Term, Roche and its Affiliates may purchase (or, in the 
          case of software, license) additional Systems in order to fully 
          utilize the Probe Arrays purchased hereunder.  Standard warranty 
          service will be provided.  In the United States such warranty 
          service will be for the longer of a) [**],  or b) the standard 
          warranty service period in the United States.  In Europe and Japan 
          such warranty service will be for a period of the longer of a) [**], 
          or b) the standard warranty service period in Europe and Japan.  
          The Systems will be installed according to a reasonable schedule 
          agreed to by Roche and AFFX, but in no event after [**], except 
          that the System to be installed in [**].

3.10      AFFX will provide Roche with reasonable training in the use of the 
          Probe Arrays at up to [**] Roche facilities for [**] per facility 
          at the time of installation of the System at such facility.  In 
          addition it is expected that [**] Roche employees per site will 
          spend [**] at AFFX in a single training program in which Roche will 
          contribute samples prepared according to AFFX protocols. Such 
          training programs at AFFX will have the "train the trainer" format 
          such that such Roche personnel will be capable of training further 
          Roche personnel.  AFFX will provide a lot of test chips at the time 
          of installation of the Systems at each of the [**] referred to in 
          Section 3.9 for training purposes at no charge.  In addition, AFFX 
          will provide test probe arrays for use in training at AFFX and test 
          probe arrays for training by Roche at Roche at a price of [**] per 
          test probe


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          array.  Roche will not use such test probe arrays for substantive data
          acquisition, and will provide reasonable forecasts of the needed
          number of test probe arrays to be purchased by Roche.

3.11      Upon written request of Roche probe sequences will be provided to 
          Roche from AFFX for up to approximately [**] on a Probe Array 
          design delivered hereunder in those cases where Roche [**].  AFFX 
          will consider in good faith a request by Roche for greater numbers 
          of probes in the event Roche has a reasonable need for such greater 
          numbers in its expression monitoring experiments.  Roche will only 
          use the probes thus provided for analysis of Roche's Probe Array 
          experiments and shall not deconstruct AFFX' probe design 
          algorithms, or use such probes in assays other than those supplied 
          by AFFX. In addition AFFX will, for quality assurance purposes, 
          provide the Committee (as defined below) with agreed documentation 
          verifying that AFFX has correctly identified probes complementary 
          to genes selected by Roche in a Target Sequence.

4         EXCLUSIVITY

4.1       During and after the Term of this Agreement, AFFX will not sell or 
          transfer the specific probe  arrays designed for Roche for a Chip 
          Project without prior written permission of Roche.  Roche may 
          choose, at its sole option and at any time during the Term, to 
          allow AFFX to transfer the probe arrays designed for Roche for a 
          Chip Project to third parties, in which case Roche will notify 
          AFFX. AFFX may, at its sole option, choose to adopt such probe 
          array designs as a commercial design that will be made available to 
          third parties, in which case AFFX will provide Roche written 
          notification of such election.  At such time as AFFX makes such 
          election, [**].  If AFFX elects to adopt a probe array design as a 
          commercial design to third parties, AFFX  will not provide probe 
          arrays of such design to third parties until [**] after the later 
          of (a) the date the first Lot of Probe Arrays of such design is 
          delivered to Roche or (b) the date of notification of AFFX's 
          election under this Section 4.1.

4.2       AFFX and its Affiliates may make, have made, and use Probe Arrays
          designed for the Chip Project for the purposes of improving its
          technology for manufacturing and using DNA


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          probe arrays and for no other purposes except as permitted by Roche
          pursuant to Section 4.1, provided that the provisions of Section 8
          will apply to any such use.

4.3       Until the end of the Resupply Term, Roche will not buy probe arrays
          directed to a Target Sequence from a third party when such third party
          probe array infringes or would infringe the patent or copyright rights
          of AFFX or its Affiliates.  In order to enforce this provision  AFFX
          must provide a) reasonable and prompt written notice to Roche of such
          infringement upon AFFX becoming aware of such use of AFFX proprietary
          rights, and b) reasonable evidence of such infringement.  This
          paragraph shall not confer on Roche or any third party any rights
          under the patent rights of AFFX.


5         COMPENSATION

5.1       Subject to Section 5.2 below, Roche shall pay to AFFX a non-refundable
          fee of [**] according to the following payment schedule:


              [**]

5.2       In the event that AFFX is unable to fabricate its anticipated Probe 
          Arrays containing approximately [**] in a manner that meets the 
          Fabrication Verification Criteria by [**] (assuming Roche 
          appropriately delivers a Target Sequence to AFFX), [**] and the end 
          of the initial Term of this Agreement (before renewal or entry to 
          the Resupply Term) as defined in Section 2.17 shall be moved back 
          by one half the number of such days, and all payments for extension 
          of the Term pursuant to Sections 5.6 and 5.7 shall be moved back by 
          one half the number of such days.  In each successive



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          quarter until AFFX is able to provide such [**] arrays, the next 
          quarterly payment shall be similarly deferred and the initial Term 
          shall be similarly extended.  By [**] the Committee will meet and 
          Roche will advise the Committee, in writing, if it reasonably 
          believes AFFX has not consistently and on a reasonably timely basis 
          delivered high density Probe Arrays [**], indicating the specific 
          deficiencies in orders on which quantity commitments of such Probe 
          Arrays were not met, along with notification that it intends to 
          terminate this Agreement.  If AFFX does not, by [**], provide to 
          Roche such Probe Arrays Roche may thereafter terminate this 
          Agreement by providing written notice by [**], and this Agreement 
          will, upon such notification, be terminated.

5.3       For each Chip Project, Roche will pay to AFFX a non-refundable 
          design fee of [**] upon delivery of the first Lot of Probe Arrays 
          which meet the Fabrication Verification Criteria for each Chip 
          Project, provided however that in the event AFFX generates designs 
          for a third party at less than [**] under similar commercial terms, 
          AFFX will give Roche the benefit of such lower rate.

5.4       For each Probe Array delivered to Roche or its Affiliates that meet
          the Fabrication Verification Criteria,  Roche will pay a fixed fee of
          [**], provided, however, that in the event that Standard Configuration
          Expression Probe Arrays are made available to third parties at a rate
          less than [**] under similar commercial terms, AFFX will give Roche
          the benefit of such lower rate.  Other Standard Configuration Probe
          Arrays will be made available at the price set for Probe Arrays herein
          or the catalog price for such Other Standard Configuration Probe
          Arrays, whichever is less.

5.4.1     AFFX will maintain a running record of the average variance from 
          the delivery times specified in Section 3.3.   In the event that 
          the average delivery time in any calendar quarter for Probe Arrays 
          delivered to Roche is more than [**] more than the times specified 
          in Section 3.3, the price of all Probe Arrays scheduled to be 
          delivered during the next quarter shall be decreased by [**] for 
          each business day that such average is more than [**] late.

5.5       The prices otherwise set forth herein include [**] new Systems in 
          configurations generally sold/licensed by AFFX to third parties.  
          Such Systems will be sold/licensed pursuant to such standard 
          commercial terms and conditions, except that the financial terms 
          will be as provided herein.  Additional Systems will be 
          sold/licensed to Roche at standard commercial prices, which are 
          currently [**] per system. If Systems are made available


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          to third parties by AFFX under substantially the same terms and
          conditions as this Agreement but for lower prices, AFFX will extend to
          Roche such lower prices.

5.6       Roche may extend the Term of this Agreement for up to two years (in
          one year increments) upon written notification to AFFX prior to twelve
          months before the end of the Term of the Agreement.  Upon Roche's
          extension of the terms for such additional one or two years, Roche
          will pay to AFFX an additional annual fee of [**]. For purposes
          of clarity in this Section, Roche may elect, at its option, to such
          extension for either one or two years, or may elect to extend for one
          year and, thereafter, elect to extend for a second year by notifying
          AFFX of such second extension twelve months before the end of the
          first extension.  Such fee will be payable in installments as follows
          if the Term is extended one year:


                [**]


          and the following additional fees will be payable if the Term is
          extended an additional one year:


                [**]


5.7       In the event that Roche wishes to provide for the supply of Probe 
          Arrays during the Resupply Term that have been ordered by Roche 
          before the end of the Term, Roche may do so upon payment of an 
          extension fee of [**] per year for up to 3 years. Such payments 
          will be made in quarterly installments.  Notice of such extension 
          must be given 1 year before the end of the Term of this Agreement 
          or the then current Resupply Term. Such payment will be due at the 
          beginning of each contract year during the Resupply Term.   During 
          the Resupply Term, Roche may order, and AFFX will supply, only 
          those Probe Arrays that have been ordered by Roche during the Term, 
          as well as Standard Configuration Expression Probe Arrays and/or 
          Other Standard Probe Arrays (if any).  During the Resupply Term, 
          Probe Arrays will be sold to Roche at [**] per Probe Array [**].  
          As to those Probe Arrays that represent [**] genes, Roche will


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          additionally pay a fee representing the information content of such
          Probe Arrays.  The information content fee for the Resupply Terms will
          be determined as follows.  [**]

          [**]

          [**]

5.8       All amounts referred to in this Section 5 will be invoiced by AFFX
          when due.  All Probe Arrays will be deemed accepted unless they are
          returned to AFFX within 30 days of delivery to Roche, with written
          explanation of the basis on which such Probe Arrays have been
          returned. All payments will be made to AFFX thirty (30) days from the
          date of invoicing by AFFX.  Late payments shall bear interest at the
          rate of (i) the average one month London Interbank Offered Rates as
          reported by Datastream from time to time plus one (1) percent; or (ii)
          or the highest rate allowed by law, whichever is less.  All payments
          in this Agreement will be made in the form a check or wire transfer to
          AFFX in U.S. Dollars.

6         INTELLECTUAL PROPERTY

6.1       Any invention made during the course of and as part of this Agreement
          shall be owned according to inventorship of the relevant applications,
          provided that Roche agrees to assign to AFFX at AFFX' cost all Chip
          Improvement Inventions.  Roche agrees to communicate periodically
          technology improvements and developments relating to probe array
          technology to the Committee.

6.2       In exchange of Roche assigning to AFFX all Chip Improvement Inventions
          AFFX agrees with the following:

6.2.1     AFFX grants Roche and its Affiliates a royalty free, irrevocable
          immunity from suit under any Chip Improvement Invention assigned to it
          pursuant to Section 6.1, provided that no



                                          16


[**] = Indicates portion redacted pursuant to the Confidential Treatment 
       Request.
<PAGE>

          rights in AFFX background technology are provided herein.  This
          Section will apply to AFFX and its successors in interest.

6.2.2     During the Term and the Resupply Term, AFFX will supply Roche at
          Roche's request with probe arrays based on Chip Improvement Inventions
          assigned by Roche to AFFX, taking into account [**].

6.3       Roche agrees to negotiate in good faith for at least non-exclusive
          access to AFFX under reasonable terms and conditions to all  Roche
          owned inventions that are directed to particular genetic sequences
          that were discovered through use of the Probe Arrays delivered
          hereunder, and such access will only be granted in the field of probe
          arrays.  Such access will be negotiated to include commercially
          reasonable royalty payments, and need only be provided if legally
          licensable at the time the invention is made.

6.4       AFFX grants to Roche a non-exclusive, royalty free, right and 
          license to use the GeneChip software in association with the Probe 
          Arrays. Such license will be for use of the GeneChip software on 
          the workstations provided with the Systems during the Term of this 
          Agreement and during the Resupply Term, if applicable.  Additional 
          copies may be purchased at [**] per copy.  [**]  GeneChip software 
          delivered with the Systems will be updated periodically during the 
          Term to be maintained in its then current commercially available 
          form. Support delivered with the Systems will be provided to Roche 
          through a single individual designated by Roche at each of such 
          facilities. Software will be licensed subject to conventional  
          software license terms and conditions.

6.5       The software provided to Roche pursuant to this Agreement will include
          AFFX' standard GeneChip software packages.  AFFX agrees [**].

7         PROJECT COORDINATION


                                          17


[**] = Indicates portion redacted pursuant to the Confidential Treatment 
       Request.
<PAGE>


7.1       AFFX will provide Roche with up to [**] of support as outlined in
          this Section at no additional charge during the Term of this
          Agreement.

7.2       Support will be provided in the form of at least one project manager
          who will coordinate and schedule all substantive interactions with
          Roche in performance of this Agreement.  In addition, support will be
          provided in the form of a scientific liaison professional and at least
          one instrumentation support professional.

7.3       If Roche desires, additional support will be provided to Roche in 
          the form of additional funded FTEs at the rate of [**] per year for 
          up to [**].  The cost of support above the [**] will be invoiced 
          each quarter by AFFX and, in the event that the support 
          requirements are expected to exceed the included level of [**] in 
          the next quarter, AFFX will provide Roche with reasonable notice 
          and justification for the need for such support.

7.4       The parties will form the Committee to aid in coordinating the
          performance of this Agreement.  The Committee will have general
          responsibility for directing the day to day performance of this
          Agreement pursuant to the terms of this Agreement.  The Committee
          shall be composed of such representatives of AFFX and Roche as each
          shall respectively appoint, including the AFFX designated project
          manager, and each Party by its representative(s) shall cast one vote
          on the Committee.  A quorum shall consist of at least one Committee
          representative from each Party.  The Committee shall act only with the
          concurring votes of both Parties.  A Party's representatives shall
          serve at the discretion of such Party and may be substituted for or
          replaced at any time by such Party.  The Committee shall meet at least
          quarterly per Contract Year during the Term.  The site of such
          meetings shall alternate between the offices of AFFX and Roche, or be
          arranged by video conference (or any other site mutually agreed upon
          by the Parties).  The proceedings of all meetings of the Committee
          shall be summarized in writing and sent to both Parties. In the event
          that the Committee is unable to reach a decision by unanimous action
          with respect to any matter and such inability continues for a period
          of forty-five (45) days after the date on which the matter is first
          submitted to the Committee, each Party shall refer the matter to
          senior management (not on the Committee) of AFFX and Roche for
          resolution. Each Party shall set forth in writing a proposed solution
          to the impasse and, if a compromise solution is not achieved within
          fifteen (15) days after the date on which the matter is referred to
          senior management, either Party may request that the more suitable of
          the two proposed solutions as finally submitted by the Parties be
          reasonably reviewed and acted upon by the Head of Global Roche
          Research.   If AFFX is not satisfied with the decision of the Head of
          Global Roche Research, AFFX may choose to arbitrate the issue(s) in
          accordance with Section


                                          18


[**] = Indicates portion redacted pursuant to the Confidential Treatment 
       Request.
<PAGE>

          12.5.  The Parties shall use reasonable efforts to otherwise use
          reasonable efforts to continue performance of this Agreement during
          any such dispute.

8         CONFIDENTIALITY

8.1       For a period of 5 years from disclosure to the other Party, each Party
          shall maintain the Confidential Information of the other Party in
          confidence (including the terms of this Agreement), and shall not
          disclose, divulge, or otherwise communicate such Confidential
          Information of the other, or use it for any purpose, except as
          permitted or contemplated by this Agreement, and in order to carry out
          the terms and objectives of this Agreement.  The Parties will use
          reasonable precautions to prevent and restrain the unauthorized
          disclosure of such Confidential Information of the other Party.  The
          provisions of this paragraph shall not apply to Confidential
          Information which:

8.1.1     was known or used by the receiving Party or its Affiliates prior to
          its date of disclosure to the receiving Party, as evidenced by the
          prior written records of the receiving Party or its Affiliates; or

8.1.2     either before or after the date of the disclosure to the receiving
          Party is lawfully disclosed without restriction on disclosure to the
          receiving Party or its Affiliates by an independent, unaffiliated
          third party rightfully in possession of the Confidential Information,
          provided that if such Confidential Information is provided to the
          receiving Party by a third party rightfully in possession of the
          Confidential Information, but with restrictions on disclosure, the
          receiving Party may use such Confidential Information in accordance
          with such restrictions of the third party;

8.1.3     either before or after the date of the disclosure to the receiving
          Party becomes published or generally known to the public through no
          fault or omission of the receiving Party or its Affiliates;


8.1.4     is required to be disclosed by the receiving Party or its Affiliates
          to comply with applicable laws, to comply with a court order, or to
          comply with governmental regulations, provided that the receiving
          Party provides prior written notice of such disclosure to the other
          Party and takes reasonable and lawful actions to avoid and/or minimize
          the degree of such disclosure;

8.1.5     is independently developed by the receiving Party or its Affiliates
          without reference to the Confidential Information.


                                          19
<PAGE>


8.2       AFFX may not publish the results of use of the Probe Arrays without
          approval of Roche.  Roche may at its option publish results of the use
          of the Probe Arrays.  Subject to the limitations of Section 3 above
          Roche may publish the results of its research at its sole discretion.
          In the event that Roche chooses to publish such results, if AFFX
          scientists have contributed to such work, authorship will be according
          to scientific input and AFFX will cooperate in such publications.  If
          it is decided that publications will be made pursuant to this Section,
          AFFX and Roche will provide the other Party draft versions of all
          publications reporting results of the use of the Probe Arrays, and
          will provide at least 60 days for technical review thereof, and to
          allow for removal of Confidential Information.

9         WARRANTY

9.1       Both Parties to this Agreement represent and warrant that they have
          the full right and authority to enter into and perform this Agreement.


9.2       AFFX warrants that the Probe Arrays delivered hereunder do not
          incorporate the trade secret or copyright rights of a third party.
          AFFX warrants that the Probe Arrays have not been the subject of
          patent assertions, or independently identified as presenting patent
          issues by AFFX, other than those disclosed to Roche legal counsel or
          otherwise licensed for use in the Probe Arrays.  AFFX DISCLAIMS ALL
          OTHER REPRESENTATIONS AND WARRANTIES, EXPRESS OR IMPLIED, INCLUDING,
          BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
          FITNESS FOR A PARTICULAR PURPOSE.  [**].  Roche understands that 
          the risks of loss herein are reflected in the price of the Probe 
          Arrays and that the terms would have been different if there had 
          been a different allocation of risk.

10        INDEMNITY

10.1      AFFX will settle or defend any suit or proceeding brought against
          Roche [**]


                                          20


[**] = Indicates portion redacted pursuant to the Confidential Treatment 
       Request.
<PAGE>



          For this paragraph to apply the indemnified Party must inform 
          the indemnifying Party within [**] days of any claim or suit being 
          made or brought, and give the indemnifying Party the full 
          authority, information, and assistance necessary to settle or 
          defend such suit or proceeding.  The indemnifying Party shall not 
          be bound in any manner by any settlement made without its prior 
          written consent. [**] This paragraph states the entire liability 
          for infringement of intellectual property rights and is in lieu of 
          all other warranties, express or implied except as stated in 
          Section 9.2.

11        TERM AND TERMINATION

11.1      This Agreement shall extend until the end of the Term, except that
          AFFX will be obligated to continue to supply Probe Arrays pursuant to
          Section 5.7 until the end of the Resupply Term.

11.2      Upon breach, the nonbreaching Party shall be entitled (but not
          required) to terminate this Agreement.  To terminate this Agreement,
          the nonbreaching Party shall provide written


                                          21


[**] = Indicates portion redacted pursuant to the Confidential Treatment 
       Request.
<PAGE>

          notice to the other Party.  Such notice shall specifically state that
          the nonbreaching Party intends to terminate this Agreement.  In the
          event that the other Party remains in breach sixty (60) days after
          such written notice by the nonbreaching Party, this Agreement shall be
          terminated, and in the event of breach by AFFX, future payments under
          Section 5.1, 5.6, and the annual fees in Section 5.7 will not be
          payable.

11.3      Upon termination of this due to expiration of the Term or termination
          by a Party for breach pursuant to Section 5.2 or 11.2, Roche may
          continue to use the Systems provided herein on Probe Arrays previously
          purchased by Roche within their specified shelf life. Roche
          understands that no license is conveyed implied for use of the Systems
          herein for Probe Arrays other than those manufactured or licensed by
          AFFX.

11.4      Upon termination of this Agreement, the following provisions will
          survive:  3.6, 4.1, 6, 8, 9.2, 10, and 12,

12        MISCELLANEOUS

12.1      Roche UNDERSTANDS THAT THE PROBE ARRAYS DELIVERED HEREUNDER ARE NOT
          FDA APPROVED.  Roche AGREES NOT TO USE THE PROBE ARRAYS DELIVERED
          HEREUNDER IN ANY CLINICAL OR OTHER SETTING REQUIRING FDA REVIEW OR
          APPROVAL EXCEPT THAT Roche MAY USE THE PROBE ARRAYS IN CLINICAL TRIALS
          WHEN IT OBTAINS ALL REQUIRED FDA OR OTHER REGULATORY APPROVALS
          REQUIRED FOR USE IN SUCH TRIALS.  Roche WILL INDEMNIFY AFFX FOR ANY
          CLAIMS MADE BY A PATIENT ARISING FROM THE USE OF THE PROBE ARRAYS.

12.2      Neither Party nor any of its Affiliates shall originate any news
          relating to this Agreement without the prior written approval of the
          other Party, which approval shall not be unreasonably withheld, except
          as otherwise required by law.

12.3      Neither Party shall assign any rights or obligations of this
          Agreement, except to a party who acquires all or substantially all of
          the relevant assets of the assigning Party by merger or sale, of
          assets or otherwise.

12.4      This Agreement shall be construed according to the laws of California
          without regard to conflict of law provisions.


                                          22
<PAGE>

12.5      In the event of any controversy or claim relating to, arising out of
          or in any way connected to any provision of this Agreement
          ("Dispute"), the Parties shall seek to settle their differences
          amicably between themselves.  Any unresolved Dispute shall be finally
          resolved by final and binding arbitration.  Whenever a Party shall
          decide to institute arbitration proceedings, it shall give written
          notice to that effect to the other Party.  The Party giving such
          notice shall refrain from instituting the arbitration proceedings for
          a period of ten (10) days following such notice to allow the Parties
          to attempt to resolve the Dispute between themselves.  If the Parties
          are still unable to resolve the dispute, the Party giving notice may
          institute the arbitration proceeding under the rules of the
          International Chamber of Commerce ("ICC Rules").  Arbitration shall be
          held in Palo Alto, California.  The arbitration shall be conducted
          before a single arbitrator mutually chosen by the Parties, but if the
          parties have not agreed upon a single arbitrator within fifteen (15)
          days after notice of the institution of the arbitration proceeding,
          then the arbitration will be conducted by a panel of three
          arbitrators.  In such case, each Party shall within thirty (30) days
          after notice of the institution of the arbitration proceedings appoint
          one arbitrator.  The presiding arbitrator shall then be appointed in
          accordance with ICC Rules.  All arbitrator(s) eligible to conduct the
          arbitration must undertake in writing as a condition of service to
          render their opinion(s) promptly after the final arbitration hearing.
          No arbitrator (nor the panel of arbitrators) shall have the power to
          award punitive damages or any award of multiple damages under this
          Agreement and such awards are expressly prohibited.  Decisions of the
          arbitrator(s) shall be final and binding on the Parties.  Judgment on
          the award of the arbitrator(s) may be entered in any court having
          jurisdiction thereof.  Except to the extent entry of judgment and any
          subsequent enforcement may require disclosure, all matters relating to
          the arbitration, including the award, shall be held in confidence by
          the Parties.

12.6      The waiver by either Party of a breach or a default of any provision
          of this Agreement by the other Party shall not be construed as a
          waiver of any succeeding breach of the same or any other provision,
          nor shall any delay or omission on the part of either Party to
          exercise or avail itself of any right power or privilege that it has
          or may have hereunder operate as a waiver of any right, power or
          privilege by such Party.

12.7      This Agreement and the documents referred to herein are the full
          understanding of the Parties with respect to the subject matter hereof
          and supersede all prior understandings and writings relating to the
          subject matter herein.  No waiver alteration or modification of any of
          the provisions herein shall be binding unless in writing and signed by
          the Parties by their respective officers.


                                          23
<PAGE>

12.8      The headings in this Agreement are for convenience only and shall not
          be considered in construing this Agreement.

12.9      In the event that any provision of this Agreement is held by a court
          of competent jurisdiction to be unenforceable because it is invalid or
          in conflict with any law of any relevant jurisdiction, the validity of
          the remaining provisions shall not be affected, and the rights and
          obligations of the Parties shall be construed and enforced as if the
          Agreement did not contain the particular provision(s) held to be
          unenforceable.

12.10     This Agreement shall be binding on and inure to the benefit of the
          Parties and their successors and permitted assigns.

12.11     None of the provisions of this Agreement shall be for the benefit of
          or enforceable by any third party.

12.12     Any notice required under this Agreement shall be made by overnight
          mail or courier to the addresses below

          If to Roche:

                Hoffmann-La Roche Inc.
                340 Kingsland Street
                Nutley, New Jersey 07110, USA
                ATTN: Corporate Secretary
          with a copy to:

                F. Hoffmann-La Roche Ltd
                Grenzacherstrasse 124
                CH 4070 Basel, Switzerland
                ATTN: Corporate Law
          and:

                Roche Bioscience, a division of Syntex (U.S.A.) Inc.
                3401 Hillview Avenue
                Palo Alto, CA  94304
                Attn:  President
          and:
                Roche Bioscience, a division of Syntex (U.S.A.) Inc.



                                          24
<PAGE>

                3401 Hillview Avenue
                Palo Alto, CA  94304
                Attn:  Legal Affairs

          If to AFFX:

                Affymetrix, Inc.
                3380 Central Expressway
                Santa Clara, California  95051
                Attn:  President


12.13     The Parties shall not be liable for delay or nonperformance if
          performance is rendered impracticable by the occurrence of any
          condition beyond the reasonable control of a Party, if such Party has
          used reasonable efforts to avoid such occurrence.  Such Party shall
          give notice to the other Party in writing promptly, and thereupon the
          affected Party's performance shall be excused and the time for
          performance shall be extended for the period of delay or inability to
          perform due to the occurrence.

12.14     This Agreement may be executed in any number of counterparts, each of
          which shall be deemed an original but all of which together shall
          constitute one and the same instrument.

                                          25
<PAGE>


IN WITNESS WHEREOF, the Parties hereto have caused this Agreement to be executed
by their properly and duly authorized officers or representatives as set forth
below.

Affymetrix, Inc.

- -------------------------
By:
   ----------------------
Date:
     --------------------

F. Hoffmann-La Roche Ltd                Hoffmann-La Roche Inc.

- -------------------------               ------------------------
By:                                  By:
   ----------------------               ------------------------
Date:                              Date:
     --------------------               ------------------------

F. Hoffmann-La Roche Ltd

- -------------------------
By:
   ----------------------
Date:
     --------------------

Syntex (U.S.A.) Inc.

- -------------------------
By:
   ----------------------
Date:
     --------------------



                                          26
<PAGE>

                                      EXHIBIT A
                          Fabrication Verification Criteria

Probes will be laid out by AFFX on substrates according to AFFX' most recent,
reliable layout software.  [**]

During the Term of the Agreement, these Fabrication Verification Criteria will
be reasonably modified by the Parties in accordance with improved verification
criteria.  In addition, AFFX will provide the specific protocols used by AFFX in
quality assurance to Roche at any time during the  Term so that Roche may ensure
proper fabrication of the Probe Arrays.


                                          27


[**] = Indicates portion redacted pursuant to the Confidential Treatment 
       Request.

<PAGE>

                              FOURTH AMENDMENT TO LEASE

This fourth amendment to lease ("Fourth Amendment") is made this 31 day of May,
1996 by and between Sobrato Interests, a California limited partnership
("Landlord") and Affymetrix, a California Corporation ("Tenant"), as successor
lessee from Affymax Research Institute ("Affymax").

                                      WITNESSETH

WHEREAS Landlord and Affymax entered into a lease dated March 5, 1992, a First
Amendment to Lease dated December 23, 1992, a Second Amendment to Lease dated
February 7, 1994 and a Third Amendment to Lease dated April 5, 1995
(collectively the "Lease") for the premises ("Premises") located at 3380 Central
Expressway, Santa Clara, California; and

WHEREAS Tenant was a subtenant under Affymax as to the entire Premises under the
Lease and the sublease was terminated and Tenant has become the Tenant under the
Lease in place of Affymax, and;

WHEREAS effective the date of this Fourth Amendment, Landlord and Tenant wish to
modify the Lease to (i) reflect Tenant's exercise of its option to extend the
term as defined in paragraph 2 of the Third Amendment to Lease, (ii) revise the
Option Term as defined in Lease paragraph 36, and (iii) delete the references to
the 3410 Central lease;

NOW, THEREFORE, in order to effect the intent of the parties as set forth above
and for good and valuable consideration exchanged between the parties, the Lease
is amended as follows:

1.  The term of the Lease is extended by 82 months so as to provide for an
Expiration Date of August 31, 2003.

2.  Base Monthly Rent during the option period shall be according to the
following:

    November 1, 1996 through August 31,1998:          $44,505.60 per month

    September 1, 1998 through August 31, 2003:        $52,001.28 per month

3.  The Option Term as defined in Lease paragraph 36 is changed from twelve
(12) months to thirty-six (36) months.

4.  Paragraph 3 of the First Amendment to Lease is hereby deleted in its
entirety which paragraph provided that if the Tenant exercises its option to
extend, the Lease shall be revised to conform to the provisions of the Lease
with the terms and conditions of the 3410 Central lease ("3410 Central Lease"). 
In addition, the cross default provisions of 

                                          1
<PAGE>

the Lease are deleted whereby a default on the 3410 Lease is a default upon the
Lease and a default on the Lease is a default on the 3410 Lease.

5.  All defined terms shall have the same meanings as in the Lease, except as
otherwise stated in this Fourth Amendment.

6.  Except as hereby amended, the Lease and all of the terms, covenants and
conditions thereof shall remain unmodified and in full force and effect.  In the
event of any conflict or inconsistency between the terms and provisions of this
Fourth Amendment and the terms and provisions of the Lease, the terms and
provisions of this Fourth Amendment shall prevail.

IN WITNESS WHEREOF, the parties hereto have set their hands to this Fourth
Amendment as of the day and date first above written.

LANDLORD:  Sobrato Interests,          TENANT:  Affymetrix, Inc.
a California limited Partnership       a California corporation

By:                                    By:  
   -------------------------------        -------------------------------
Its:                                   Its: 
   -------------------------------         ------------------------------


                                          2

<PAGE>

                                    LEASE BETWEEN
                           SOBRATO INTERESTS AND AFFYMETRIX

SECTION                                                         PAGE #
- -------                                                         ------


                                          i


<PAGE>

                                  TABLE OF CONTENTS


1.   PARTIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
2.   PREMISES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
3.   USE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
4.   TERM AND RENTAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
5.   LATE CHARGES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
6.   POSSESSION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
7.   ACCEPTANCE OF POSSESSION AND COVENANTS TO SURRENDER . . . . . . . . . . .2
8.   USES PROHIBITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
9.   ALTERATIONS AND ADDITIONS . . . . . . . . . . . . . . . . . . . . . . . .4
10.  MAINTENANCE OF PREMISES . . . . . . . . . . . . . . . . . . . . . . . . .4
A.   Landlord and Tenant's Obligations Regarding Common Area Costs . . . . . .4
B.   Common Area Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
C.   Tenant's Allocable Share. . . . . . . . . . . . . . . . . . . . . . . . .5
D.   Waiver of Liability . . . . . . . . . . . . . . . . . . . . . . . . . . .6
E.   Tenant's Obligations. . . . . . . . . . . . . . . . . . . . . . . . . . .6
11.  HAZARD INSURANCE. . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
A.   Tenant's Use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
B.   Landlord's Insurance. . . . . . . . . . . . . . . . . . . . . . . . . . .7
C.   Tenant's Insurance. . . . . . . . . . . . . . . . . . . . . . . . . . . .8
D.   Waiver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
12.  TAXES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
13.  UTILITIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9


                                          ii
<PAGE>

14.   ABANDONMENT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
15.   FREE FROM LIENS. . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
16.   COMPLIANCE WITH GOVERNMENTAL REGULATIONS . . . . . . . . . . . . . . . .9
17.   TOXIC WASTE AND ENVIRONMENTAL DAMAGE. . . . . . . . . . . . . . . . . .10
A.    Tenant's Responsibility . . . . . . . . . . . . . . . . . . . . . . . .10
B.    Tenant's Indemnity Regarding Hazardous Materials. . . . . . . . . . . .11
C.    Landlord's Indemnity Regarding Hazardous Materials. . . . . . . . . . .11
18.   INDEMNITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
19.   ADVERTISEMENTS AND SIGNS. . . . . . . . . . . . . . . . . . . . . . . .12
20.   ATTORNEY'S FEES . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
21.   TENANT'S DEFAULT. . . . . . . . . . . . . . . . . . . . . . . . . . . .12
A.    Remedies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
B.    Right to Re-enter . . . . . . . . . . . . . . . . . . . . . . . . . . .13
C.    Abandonment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
D.    No Termination. . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
22.   SURRENDER OF LEASE. . . . . . . . . . . . . . . . . . . . . . . . . . .14
23.   HABITUAL DEFAULT. . . . . . . . . . . . . . . . . . . . . . . . . . . .15
24.   LANDLORD'S DEFAULT. . . . . . . . . . . . . . . . . . . . . . . . . . .15
25.   NOTICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
26.   ENTRY BY LANDLORD . . . . . . . . . . . . . . . . . . . . . . . . . . .15
27.   DESTRUCTION OF PREMISES . . . . . . . . . . . . . . . . . . . . . . . .16
A.    Destruction by an Insured Casualty. . . . . . . . . . . . . . . . . . .16
B.    Destruction by an Uninsured Casualty. . . . . . . . . . . . . . . . . .16
28.   ASSIGNMENT OR SUBLEASE. . . . . . . . . . . . . . . . . . . . . . . . .17

                                          iii
<PAGE>

A.    Consent by Landlord . . . . . . . . . . . . . . . . . . . . . . . . . .17
B.    Assignment or Subletting Consideration. . . . . . . . . . . . . . . . .18
C.    No Release. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
D.    Effect of Default . . . . . . . . . . . . . . . . . . . . . . . . . . .19
29.   CONDEMNATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
30.   EFFECTS OF CONVEYANCE. . . . . . . . . . . . . . . . . . . . . . . . . 19
31.   SUBORDINATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
32.   WAIVER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
33.   HOLDING OVER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
34.   SUCCESSORS AND ASSIGNS . . . . . . . . . . . . . . . . . . . . . . . . 21
35.   ESTOPPEL CERTIFICATES. . . . . . . . . . . . . . . . . . . . . . . . . 21
36.   OPTION TO EXTEND THE LEASE TERM. . . . . . . . . . . . . . . . . . . . 21
A.    Grant and Exercise of Option. . . . . . . . . . . . . . . . . . . . . .21
B.    Determination of Fair Market Rental . . . . . . . . . . . . . . . . . .22
C.    Resolution of a Disagreement over the Fair Market Rental. . . . . . . .22
37.   OPTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
38.   QUIET ENJOYMENT. . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
39.   BROKERS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
40.   This section intentionally left blank . . . . . . . . . . . . . . . . .24
41.   AUTHORITY OF PARTIES. . . . . . . . . . . . . . . . . . . . . . . . . .24
42.   MISCELLANEOUS PROVISIONS. . . . . . . . . . . . . . . . . . . . . . . .24
A.    Rent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
B.    Management Fee. . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
C.    Performance by Landlord . . . . . . . . . . . . . . . . . . . . . . . .24

                                         iv
<PAGE>

D.    Interest. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
E.    Rights and Remedies . . . . . . . . . . . . . . . . . . . . . . . . . .24
F.    Survival of Indemnities . . . . . . . . . . . . . . . . . . . . . . . .24
G.    Severability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
H.    Choice of Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
I.    Time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
J.    Entire Agreement. . . . . . . . . . . . . . . . . . . . . . . . . . . .25
K.    Representations . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
L.    Headings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

                                          v
<PAGE>


     1.  PARTIES:  THIS LEASE is entered into on this 31 day of May, 1996,
between Sobrato Interests, a California limited partnership, and Affymetrix,
Inc. a California corporation, hereinafter called respectively Landlord and
Tenant.

     2.  PREMISES:  Landlord hereby leases to Tenant, and Tenant hires from
Landlord those certain Premises with the appurtenances, situated in the City of
Santa Clara, County of Santa Clara State of California, and more particularly
described as follows, to-wit:

That certain real property commonly known and designated as 3450 Central
Expressway consisting of approximately 45,360 square feet ("Building") and 159
parking stalls in a project consisting of total of five (5) buildings, including
the Premises, totaling 412,171 square feet ("Project") as outlined in red on
Exhibit "A".  The parking stalls shall be available for Tenant's exclusive use
but shall not designated or segregated from the balance of the parking area.

     3.  USE:  Tenant shall use the Premises only for the following purposes
and shall not Change the use of the Premises without the prior written consent
of Landlord: Office, research development, testing, light manufacturing,
ancillary warehouse, and related legal uses.  Landlord makes no representation
or warranty that any specific use of the Premises desired by Tenant permitted
pursuant to any Laws.

     4.  TERM AND RENTAL:  The term ("Lease Term") shall be for seventy-eight
(78) months commencing on the 31st day of March, 1997 ("Commencement Date"), and
ending on the 31st day August, 2003, ("Expiration Date").  In addition to all
other sums payable by Tenant under this Lease, Tenant shall pay base monthly
rent ("Base Monthly Rent") for the Premises according to the following schedule:

    March 1, 1997 through August 31, 1998:            $43,092.00 per month

    September 1, 1998 through August 31, 2003:        $50,349.60 per month

Base Monthly Rent shall be due on or before the first day of each calendar month
during Lease Term.  All sums payable by Tenant under this Lease shall be paid in
lawful money of the United States of America, without offset or deduction, and
shall be paid to Landlord at such place or places as may be designated from time
to time by Landlord.  Base Monthly Rent for any period less than a calendar
month shall be a pro rata portion of the monthly installment.

Concurrently with Tenant's execution of this Lease, Tenant shall pay to Landlord
the sum of Forty Three Thousand Ninety Two and No/100 Dollars ($43,092.00) as
prepaid rent for the period from March 1, 1997 to March 31, 1997.


<PAGE>

     5.  LATE CHARGES:  Tenant hereby acknowledges that late payment by Tenant
Landlord of Base Monthly Rent and other sums due hereunder will cause Landlord
to incur costs not contemplated by this Lease, the exact amount of which will be
extremely difficult to ascertain.  Such costs include, but are not limited to,
administrative, processing, accounting charges, and late charges which may be
imposed on Landlord by the terms of any contract, revolving credit, mortgage or
deed covering the Premises.  Accordingly, if any installment of Base Monthly
Rent or any other sum due from Tenant shall not be received by Landlord or
Landlord's designee within ten (10) days after a written notice from Landlord
that such amount is due, Tenant shall pay to Landlord a late charge equal to
five (5%) percent of such overdue amount which shall be due and payable with the
payment then delinquent.  Landlord agrees to waive said late charge in the event
the Base Monthly Rent or other sum due is received within five days after
receipt by Tenant of Landlord's notice to quit or pay rent.  The parties hereby
agree that such late charge represents a fair and reasonable estimate of costs
Landlord will incur by reason of late payment by Tenant.  Acceptance of such
late charge by Landlord shall in no event constitute a waiver of Tenant's
default with respect to such overdue amount, nor prevent Landlord from
exercising any of the other rights and remedies granted hereunder.  In the event
that a late charge is payable hereunder, whether or not collected, for (3)
consecutive installments of Base Monthly Rent, then rent shall automatically
become due and payable quarterly in advance, rather than monthly,
notwithstanding any provision of this Lease to the contrary.

IT IS FURTHER MUTUALLY AGREED BETWEEN THE PARTIES AS FOLLOWS:

     6.  POSSESSION:  If Landlord, for any reason whatsoever, cannot deliver
possession of said Premises to Tenant at the Commencement Date, as hereinbefore
specified, this Lease shall be void or voidable, nor shall Landlord be liable to
Tenant for any loss or damage resulting therefrom; but in that event the
commencement and termination dates of the Lease and all dates affected thereby
shall be revised to conform to the date of Landlord's delivery of possession.

The above is however, subject to the provision that the period of delay of
delivery of the Premises shall not exceed 90 days from the commencement date
herein.  If the period of delay of delivery exceeds the foregoing, Tenant, at
its option, may cancel this Lease and declare it null and void.  Notwithstanding
the foregoing, Landlord agrees to avail itself of all legal remedies to evict
the current occupant of the Premises if it does not vacate by the expiration
date of its lease.

     7.  ACCEPTANCE OF POSSESSION AND COVENANTS TO SURRENDER:  On Commencement
Date, Landlord shall deliver the keys to the Premises to Tenant and Tenant shall
accept possession from Landlord.  Landlord shall


                                          2
<PAGE>


reimburse Tenant for the costs to put the HVAC system in good condition and
repair, as detailed in an inspection report to be issued by Thermal Mechanical
within 90 days prior to the Commencement Date.  During the first 8 months of the
Lease Term, Tenant intends to make significant modifications ("Initial
Improvements") to the Premises.  Tenant shall comply with the provisions of
Lease paragraph 9 in its construction of the Initial Improvements.  The Tenant
agrees on the Expiration Date, or on the sooner termination of this Lease to
surrender the Premises to Landlord in good condition and repair, reasonable wear
and tear excepted.  "Good condition" shall mean that the interior walls, floors,
suspended ceilings, and carpeting within the Premises will be cleaned to the
same condition as existed at completion of Initial Improvements, normal wear and
tear excepted.  Tenant agrees, at its sole cost, to remove phone and data
cabling installed by Tenant from the suspended ceiling and repair or replace
broken ceiling tiles, and relevel the ceiling if required.  Tenant shall
ascertain from Landlord within (30) days before the Expiration Date whether
Landlord desires to have the Premises or any part or parts thereof restored to
their condition as of the completion of the Initial Improvements or to cause
Tenant to surrender all Alterations in Place to Landlord.  If Landlord shall so
desire, then Tenant shall remove such Alterations (except Initial Improvements)
as Landlord may require and shall repair and restore said Premises or such part
or parts thereof before the Expiration Date at Tenant's sole cost and expense.
Tenant on before the Expiration Date or sooner termination of this Lease, shall
remove all its personal property and trade fixtures from the Premises, and all
property and fixtures not so removed shall be deemed to be abandoned by Tenant.
If the Premises are not surrendered at the Expiration Date or sooner termination
of this Lease in the condition required by this paragraph, Tenant shall
indemnify, defend, and hold harmless Landlord against loss or liability
resulting from delay by Tenant in surrendering the Premises including, without
limitation, any claims made by any succeeding tenant founded on such delay.

Notwithstanding the provisions of this paragraph 7, Landlord shall at its sole
expense repair latent defects respecting the Premises.  Landlord's obligations
with respect to the correction of such defects shall be limited to the cost to
correct the defective work and Landlord shall not be liable for any
consequential damages or other loss or damage incurred by Tenant.  It is further
agreed by parties that Landlord shall have no obligation to repair HVAC or other
Building systems serving previous tenant's manufacturing and process areas,
including but not limited to wafer fabrication areas.

     8.  USES PROHIBITED:  Tenant shall not commit, or suffer to be committed,
any waste upon the said Premises, or any nuisance, or other act or thing which
may disturb the quiet enjoyment of any other tenant in or around the Building or
allow any sale by auction upon the Premises, or allow the Premises to be used
for any unlawful or objectionable purpose, or place any loads upon the floor,
walls, or ceiling which endanger the structure, or use any machinery apparatus
which will in any manner vibrate or shake the Building, or place any harmful
liquid waste materials, or hazardous materials in the


                                          3
<PAGE>

drainage system of, or upon or in the soils surrounding the Building.  No 
materials, supplies, equipment, finished products or semi-finished products, 
raw materials or articles of any nature or any waste materials, refuse, scrap 
or debris shall be stored upon or permitted to remain on any portion of the 
Premises outside of the Building proper without Landlord's prior approval, 
which approval may be withheld in its sole discretion.

     9.  ALTERATIONS AND ADDITIONS:  Tenant shall not make, or suffer to be
made, alteration or addition to the said Premises ("Alterations"), or any part
thereof, without (i) the written-consent of Landlord first had and obtained,
which consent shall not be unreasonably withheld or delayed, and (ii) delivering
to Landlord the proposed architectural and structural plans for all such
Alterations.  Any Alterations, except movable furniture and trade fixtures,
shall become at once part of the realty and belong to Landlord.  Alterations
which are not to be deemed as trade fixtures shall include heating, lighting,
electrical systems, air conditioning, partitioning, carpeting, or other
installation which has become an integral part of the Premises.  After having
obtained Landlord's consent, Tenant agrees that it will not proceed to make such
Alterations until (i) Tenant has obtained all required governmental approvals
and permits, and (ii) Tenant has provided Landlord reasonable security, in form
reasonably approved by Landlord, to protect Landlord against mechanics' lien
claims.  Tenant further agrees to provide Landlord (i) written notice of
anticipated start date and actual start date of the work, and (ii) a complete
set of half-size (15" X 21") vellum as-built drawings.  All Alterations shall be
constructed in compliance with applicable buildings codes and laws, including
Title 24 and ADA, and shall be maintained, replaced or repaired at Tenant's sole
costs and expense.

Notwithstanding the foregoing, Tenant shall be entitled without obtaining
Landlord's consent to make any alteration or addition to the Premises which does
not affect the structure of the Building, provided that each such alteration
costs no more than $15,000, and all such alterations in any twelve (12) month
period do not exceed an aggregate of $50,000.

     10. MAINTENANCE OF PREMISES:

         A.   LANDLORD AND TENANT'S OBLIGATIONS REGARDING COMMON AREA COSTS:
Landlord shall, at its sole cost and expense, maintain in good condition, order,
and repair, and replace as and when necessary, the foundation, exterior load
bearing walls and roof structure of the Building Shell.  Landlord agrees to
perform the maintenance, repair and replacement of those items defined in
paragraph 10(B) below for which Common Area Costs are incurred.  Tenant agrees
to reimburse Landlord for the expenses resulting from Landlord's payment of
Common Area Costs as defined in paragraph 10(B) incurred by Landlord because the
cost is not directly allocable to or payable by a single tenant in the Building
or the Project.  Tenant agrees to pay Tenant's Allocable Share as


                                          4
<PAGE>

defined in paragraph 10(C) of the Common Area Costs, as additional rental,
within ten (10) days of written invoice from Landlord.

         B.   COMMON AREA COSTS:  For purposes of calculating Tenant's
Allocable Share of Building and of Project Costs, the term "Common Area Costs"
shall mean all costs and expenses of the nature hereinafter described which are
incurred in connection with ownership, maintenance and operation of the Building
or the Project in which the Premises are located, as the case may be not
directly allocable to or payable by a single tenant in the Building or the
Project, together with such additional facilities as may be determined by
Landlord to be reasonably desirable or necessary to the ownership and operation
of the Building and/or Project.  All costs and expenses shall be determined in
accordance with generally accepted accounting principles which shall be
consistently applied. (with accruals appropriate to Landlord's business),
including but not limited to, the following: (i) common area utilities,
including water and power and lighting to the extent not separately metered;
(ii) common area maintenance and service agreements for the Building or the
Project and the equipment therein including, without limitation, common area
janitorial services, alarm and security services, exterior window cleaning, and
maintenance of sidewalks, landscaping, waterscape, parking areas, and driveways;
(iii) insurance premiums and costs, including without limitation, the premiums
and cost of fire, casualty and liability coverage and rental abatement and
earthquake (if commercially available) insurance applicable to the Building or
Project; (iv) repairs, replacements and general maintenance (excluding repairs
and general maintenance paid by proceeds of insurance or by Tenant or other
third parties, and repairs or alterations attributable solely to tenants of the
Building or Project other than Tenant); and (v) All real estate taxes, special
assessments, service payments in lieu of taxes, excises, transit charges,
housing fund assessment, levies, fees or charges and including any substitutes
or additions thereto which may occur during the Lease Term (and Renewal Terms,
if any) of this lease which are assessed, or imposed by any public authority
upon the Building or Project, the act of entering this Lease, the occupancy by
Tenant, the rent provided for in this Lease and including real estate tax
increases due to a sale or transfer of the Building or the Project, in which the
Premises are located, as such taxes are levied or appear on the City and County
tax bills and assessment rolls.  All special assessments shall be paid over the
longest period allowed by the taxing authority.  This shall be a Net Lease and
the Base Monthly Rent shall be paid to Landlord absolutely net of all costs and
expenses.  The provision for payment of Common Area Costs by means of periodic
payment of Tenant's allocable Share of Building and/or Project Costs are
intended to pass on to Tenant and reimburse Landlord for all costs of operating
and managing the Building and/or Project.

         C.   TENANT'S ALLOCABLE SHARE:  For purposes of prorating Common Area
Costs which Tenant shall pay, Tenant's allocable Share of Building Costs is
computed by multiplying the total Common Area Costs for services shared by the
Building by a fraction, the numerator of which is the rentable square footage of
the


                                          5
<PAGE>

Premises and the denominator of which is the total rentable square footage of
the Building (excluding common areas).  Tenant's allocable Share of Project
Costs shall be computed on a shared service by service basis, by multiplying the
total Common Area Costs for services shared by the Building and one or more
buildings in the Project by a fraction, the numerator of which is the rentable
square footage of the Premises and the denominator of which is the total
rentable square footage of the Buildings in the Project which share the
services.  It is understood and agreed by Landlord and Tenant that Tenant's
allocable Share of Building Costs is 100.00% and of Project Costs is 11.01%.  It
is understood and agreed that Tenant's obligation to share in Common Area Costs
shall be adjusted to reflect the commencement and termination dates of the Lease
Term and are subject to recalculation in the event of expansion of the Building
or Project.

         D.   WAIVER OF LIABILITY:  Failure by Landlord to perform any defined
services, or any cessation thereof, when such failure is caused by accident,
breakage, repairs, strikes, lockout or other labor disturbances or labor
disputes of any character, or by any other cause, similar or dissimilar, beyond
the reasonable- control of Landlord, shall not render Landlord liable in any
respect for damages to either person or property, nor be construed as an
eviction of Tenant, nor cause an abatement of rent nor relieve Tenant from
fulfillment of any covenant or agreement hereof.  Should any of the equipment or
machinery utilized in supplying the services listed herein break down, or for
any cause cease to function properly, upon receipt of written notice from Tenant
of any deficiency or failure of any defined Services, Landlord shall use
reasonable diligence to repair the same promptly, but Tenant shall have no right
to terminate this Lease, and shall have no claim for rebate of rent or damages,
on account of any interruptions in service occasioned thereby or resulting
therefrom.  Tenant waives the provisions of California Civil Code Sections 1941
and 1942 concerning the Landlord's obligation of tenantability and Tenant's
right to make repairs and deduct the cost of such repairs from the rent.
Landlord shall not be liable for a loss of or injury to property, however
occurring, through or in connection with or incidental to furnishing or its
failure to furnish any of the foregoing, unless such loss or injury is due to
the negligence or willful misconduct of Landlord.

         E.   TENANT'S OBLIGATIONS:  Except as provided in 10(A) above, Tenant
shall, at its sole cost, keep and maintain, repair and replace, said Premises
and appurtenances and every part hereof, including but not limited to, exterior
walls, roof membrane, glazing, plumbing, electrical and HVAC systems, and all
the Tenant Interior Improvements in good and sanitary order, condition, and
repair; normal wear and tear and damage by casualty excepted.  Tenant shall
provide Landlord with a copy of a service contract between Tenant and a licensed
air-conditioning and heating contractor which contract shall provide for
bimonthly maintenance of all air conditioning and heating equipment at the
Premises.  Tenant shall pay the cost of all air-conditioning and heating
equipment repairs or replacements which are either excluded from such service
contract


                                          6
<PAGE>

or any existing equipment warranties.  All wall surfaces and floor tile are to
be maintained in an as good a condition as when Tenant took possession free of
holes, gouges, or defacements.  Tenant agrees to limit attachments to vinyl
demountable wall surfaces exclusively to V-joints.

Tenant shall also be responsible for the preventive maintenance of the membrane
of the roof, which responsibility shall be deemed properly discharged if (i)
Tenant contracts with a licensed roof contractor who is reasonably satisfactory
to both Tenant and Landlord, at Tenant's sole cost, to inspect the roof membrane
at least every six (6) months, with the first inspection due the sixth (6th)
month after the Commencement Date, and (ii) Tenant performs, at Tenant's sole
cost, all preventive maintenance recommendations made by such contractor within
a reasonable time after such recommendations are made.  Such preventive
maintenance might include acts such as clearing storm gutters and drains,
removing debris from the roof membrane, trimming trees overhanging the roof
membrane, applying coating materials to seal roof penetrations, repairing
blisters, and other routine measures.  Tenant shall provide to Landlord a copy
of such preventive maintenance contract and paid invoices for the recommended
work.

     11. HAZARD INSURANCE:

         A.   TENANT'S USE:  Tenant shall not use, or permit said Premises, or
any part thereof, to be used, for any purpose other than that for which the said
Premises are hereby leased; and no use shall be made or permitted to be made of
the said Premises, nor acts done, which will cause an increase in premiums or a
cancellation of any insurance policy covering said Building, or any part
thereof, nor shall Tenant sell or permit to be kept, used or sold, in or all-out
said Premises, any article which may be prohibited by the standard form of fire
insurance policies.  Tenant shall, at its sole cost and expense, comply with any
and all requirements, pertaining to said Premises, of any insurance organization
or company, necessary for the maintenance of reasonable fire and public
liability insurance, covering said Building and appurtenances.

         B.   LANDLORD'S INSURANCE:  Landlord agrees to purchase and keep in
force fire and extended coverage, earthquake (at Landlord's election and at a
commercially reasonable rate), and 12 month rental loss insurance covering the
Premises in amounts not to exceed the actual insurable value of the Building as
determined by Landlord's insurance company s appraisers.  The Tenant agrees to
pay to the Landlord as additional rent, on demand, the full cost of said
insurance as evidenced by insurance billings to the Landlord, and in the event
of damage covered by said insurance, the amount of any deductible under such
policy.  Payment shall be due to Landlord within ten (10) days after written
invoice to Tenant.  Tenant consents to Landlord's current insurance deductible
of $5,000.00 and shall have the right to approve any future change in the


                                          7
<PAGE>

deductible amount.  It is understood and agreed that Tenant's obligation under
this paragraph will be prorated to reflect the commencement and termination
dates of this Lease.

         C.   TENANT'S INSURANCE:  Tenant, at its sole cost, agrees to insure
its personal property and Alterations for amounts not to exceed their actual
insurable value and to obtain worker's compensation and public liability and
property damage insurance for occurrences within the Premises with a
$5,000,000.00 combined single limit for bodily injury and property damage.
Tenant shall name Landlord and Landlord's lender as an additional insured, shall
deliver a copy of the policies and renewal certificates to Landlord.  All such
policies shall provide for thirty (30) days' prior written notice to Landlord of
any cancellation, termination, or reduction in coverage.  Notwithstanding the
above, Landlord retains the right to have Tenant provide other forms of
insurance which may be reasonably required to cover future risks.

         D.   WAIVER:  Landlord and Tenant hereby waive any and all rights each
may have against the other on account of any loss or damage occasioned to the
Landlord or the Tenant as the case may be, or to the Premises or its contents,
and which may arise from any risk covered by their respective insurance
policies, as set forth above.  The parties shall use their reasonable efforts to
obtain from their respective insurance companies a Waiver of any right of
subrogation which said insurance company may have against the Landlord or the
Tenant, as the case may be.

     12. TAXES:  Tenant shall be liable and shall pay prior to delinquency, for
all taxes and assessments levied against personal property and trade or business
fixtures, and agrees to pay, as additional rental, all real estate taxes and
assessment installments (special or general) or other impositions or charges
which may be levied on the Premises, upon the occupancy of the Premises and
including any substitute or additional charges which may be imposed during, or
applicable to the Lease Term including real estate tax increases due to a sale
or other transfer of the Premises, as they appear on the City and County tax
bills during the Lease Term, and as they become due.  It is understood and
agreed that Tenant's obligation under this paragraph will be prorated to reflect
the commencement and termination dates of this Lease.  In any time during the
Lease Term a tax, excise on rents, business license tax, or any other tax,
however described, is levied or assessed against Landlord, as a substitute in
whole or in part for taxes assessed or imposed on land or Buildings, Tenant
shall pay and discharge his pro rata share of such tax or excise on rents or
other tax before it becomes delinquent, except that this provision is not
intended to cover net income taxes, inheritance, gift or estate tax imposed upon
the Landlord.  In the event that a tax is placed, levied, or assessed against
Landlord and the taxing authority takes the position that the Tenant cannot pay
and discharge his pro rata share of such tax on behalf of the Landlord, then at
the sole election of the Landlord, the


                                          8
<PAGE>

Landlord may increase the rental charged hereunder by the exact amount of such
tax and Tenant shall pay such increase as additional rent hereunder.

     13. UTILITIES:  Tenant shall pay directly to the providing utility all
water, gas, heat, light, power, telephone and other utilities supplied to the
Premises.  Landlord shall not be liable for a loss of or injury to property,
however occurring, through or in connection with or incidental to furnishing or
failure to furnish any of utilities to the Premises and Tenant shall not be
entitled to abatement or reduction of any portion of the Base Monthly Rent so
long as any failure to provide and furnish the utilities to the Premises due to
any cause beyond the Landlord's reasonable control.

     14. ABANDONMENT:  Tenant shall not abandon the Premises at any time during
the Lease Term; and if Tenant shall abandon or surrender said Premises, or be
dispossessed by process of law, or otherwise, any personal property belonging to
Tenant and left on the Premises shall be deemed to be abandoned, at the option
of Landlord, except such property as may be mortgaged to Landlord.
Notwithstanding the foregoing, Tenant shall be entitled to suspend its
operations on the Premises and vacate the Premises provided that Tenant
continues to timely pay rent and perform all other obligations of Tenant under
this Lease, and further provided that Tenant provides a security guard or other
reasonable security protection for the Premises.

     15. FREE FROM LIENS:  Tenant shall keep the Premises and the Building free
from any liens arising out of any work performed, materials finished, or
obligations incurred by Tenant or claimed to have been performed for Tenant.  In
the event Tenant fails to discharge any such lien within ten (10) days after
receiving notice of the filing, Landlord shall be entitled to discharge such
lien at Tenant's expense and all resulting costs incurred by Landlord, including
attorney's fees shall be due from Tenant as additional rent.

Notwithstanding the provisions of this paragraph 15, Tenant shall have the right
to contest such liens if Tenant obtains a bond equal to 150% of the amount of
such lien to prevent enforcement of the lien during such contest or otherwise
makes adequate provision to prevent enforcement of the lien during such contest.

     16. COMPLIANCE WITH GOVERNMENTAL REGULATIONS:  Tenant shall, at its sole
cost and expense, comply with all of the requirements of all Municipal, State
and Federal authorities now in force, or which may hereafter be in force,
pertaining to the said Premises, and shall faithfully observe in the use of the
Premises all Municipal ordinances and State and Federal statutes now in force or
which may hereafter be in force.  The judgment of any court of competent
jurisdiction, or the admission of Tenant in any action or proceeding against
Tenant, whether Landlord be a party thereto or not, that


                                          9
<PAGE>

Tenant has violated any such ordinance or statute in the use of the Premises,
shall be conclusive of that fact as between Landlord and Tenant.

Notwithstanding the provisions of this paragraph 16 and excepting Title 24 and
ADA work for which Tenant is responsible, if any improvement or alteration to
the Premises is required as a result of any future laws or regulations affecting
the Premises not related to Tenant's specific use of the Premises, and provided
further said improvement or alteration is not required because of alterations to
the Premises made by Tenant, the cost of such improvements shall be allocated
between Landlord and Tenant such that Tenant shall pay to Landlord upon
completion of such improvement, the portion of the cost thereof equal to the
remaining number of years in the lease term divided by the anticipated useful
life of such improvement.  Landlord represents and warrants, to the best of its
knowledge, that the Building shell applies with all building codes that were
applicable as of the date of its construction.

     17. TOXIC WASTE AND ENVIRONMENTAL DAMAGE:

         A.   TENANT'S RESPONSIBILITY:  Without the prior written consent of
Landlord, Tenant shall not bring, use, or permit upon the Premises, or generate,
emit, or dispose from the Premises any chemicals, toxic or hazardous gaseous,
liquid or solid materials or waste, including without limitation, material or
substance having characteristics of ignitability, corrosivity, reactivity, or
toxicity or substances or materials which are listed on any of the Environmental
Protection Agency's lists of hazardous wastes or which are identified in
Sections 66680 through 66685 of Title 22 of the California Administrative Code
as the same may be amended from time to time ("Hazardous Materials").  In order
to obtain consent, Tenant shall deliver to Landlord its written proposal
describing the toxic material to be brought onto the Premises, measures to be
taken for storage and disposal thereof, safety measures to be employed to
prevent pollution of the air, ground, surface and ground water.  Landlord
consents to Tenant's use of Hazardous Materials on the Premises on the condition
that Tenant represents and warrants that Tenant will (i) adhere to an reporting
and inspection requirements imposed by Federal, State, County or Municipal laws,
ordinances or regulations and will provide Landlord a copy of any such reports
or agency inspections, (ii) obtain and provide Landlord copies of all necessary
permits required for the use and handling Hazardous Materials on the Premises,
(iii) enforce Hazardous Materials handling and disposal practices consistent
with industry standards, and (iv) properly close the facility with regard to
Hazardous Materials including the removal or decontamination of any process
piping, mechanical ducting, storage tanks, containers, or trenches which have
come into contact with Hazardous Materials and obtain a closure certificate from
the local administering agency prior to the Expiration Date.  Landlord may
employ an independent engineer or consultant to periodically inspect Tenant's
operations to verify that Tenant is complying with its obligations under this
paragraph.  In the event it is determined by


                                          10
<PAGE>

Landlord's consultant that Tenant is in material violation with respect to its
obligations under this paragraph and such violation has not previously been
reported by Tenant or has not been cured, then Tenant shall pay the reasonable
future expense of employing Landlord's independent engineer or consultant to
periodically inspect Tenant's operations.  The forgoing right of inspection
shall be exercised by Landlord only if Landlord believes it may be subject to
liability because of Tenant's handling of hazardous materials.

         B.   TENANT'S INDEMNITY REGARDING HAZARDOUS MATERIALS:  Tenant shall
comply, at its sole cost, with all laws pertaining to, and shall indemnify and
hold Landlord harmless from any claims, liabilities, costs or expenses incurred
or suffered by Landlord, except through Landlord's negligence or willful
misconduct, arising from such bringing, using, permitting, generating, emitting
or disposing of Hazardous Materials.  Tenant's indemnification and hold harmless
obligations include, without limitation, (i) claims, liability, costs or
expenses resulting from or based upon administrative, judicial (civil or
criminal) or other action, legal or equitable, brought by any private or public
person under common law or under the Comprehensive Environmental Response,
Compensation and Liability Act of 1980 ("CERCLA"), the Resource Conservation and
Recovery Act of 1980 ("RCRA") or any other Federal, State, County or Municipal
law, ordinance or regulation, (ii) claims, liabilities, costs or expenses
pertaining to the identification, monitoring, cleanup, containment, or removal
of Hazardous Materials from soils, riverbeds or aquifers including the provision
of an alternative public drinking water source, and (iii) all costs of defending
such claims.

         C.   LANDLORD'S INDEMNITY REGARDING HAZARDOUS MATERIALS:  Landlord
shall indemnify and hold Tenant harmless from any claims, liabilities, costs or
expenses incurred or suffered by Tenant related to the removal, investigation,
monitoring or remediation of Hazardous Materials which are present or which come
to be present on the Premises through no fault of Tenant.  Landlord's
indemnification and hold harmless obligations include, without limitation, (i)
claims, liability, costs or expenses resulting from or based upon
administrative, judicial (civil or criminal) or other action, legal or
equitable, brought by any private or public person under common law or under the
Comprehensive Environmental Response, Compensation and Liability Act of 1980
("CERCLA"), the Resource Conservation and Recovery Act of 1980 ("RCRA") or any
other Federal, State, County or Municipal law, ordinance or regulation, (ii)
claims, liabilities, costs or expenses pertaining to the identification,
monitoring, cleanup, containment, or removal of Hazardous Materials from soils,
riverbeds or aquifers including the provision of an alternative public drinking
water source, and (iii) all costs of defending such claims.  In no event shall
Landlord be liable for any consequential damages suffered or incurred by Tenant
as a result of any such contamination.

     18. INDEMNITY:  As a material part of the consideration to be rendered to
Landlord, Tenant hereby waives all claims against Landlord for damages to goods,
wares-


                                          11
<PAGE>

and merchandise, and all other personal property in, upon or about said
Building, for injuries to persons in or about said Building, or for injuries or
claims by Tenant's agents or invitees in or about the Project, from any cause
arising at any time except due to the negligence or willful misconduct of
Landlord, and Tenant will hold Landlord exempt and harmless from any damage or
injury to any person, or to the goods, wares and merchandise and all other
personal property of any person, arising from the use of the Premises by Tenant,
or from the failure of Tenant to keep the Building in good condition and repair,
as herein provided.  Further, in the event Landlord is made party to any
litigation due to the acts or omission of Tenant, Tenant will indemnify and hold
Landlord harmless from any such claim or liability including Landlord's costs
and expenses and reasonable attorney's fees incurred in defending such claims.

     19. ADVERTISEMENTS AND SIGNS:  Tenant will not place or permit to be
placed, in, upon or about the said Premises any unusual or extraordinary signs,
or any signs not approved by the city or other governing authority.  The Tenant
will not place, or permit to be placed, upon the Premises, any signs,
advertisements or notices without the written consent of the Landlord as to
type, size, design, lettering, coloring and location, and such consent will not
be unreasonably withheld.  Any sign so placed on the Premises shall be removed
by Tenant, at its expense, prior to the Expiration Date or promptly following
the earlier termination of the lease and Tenant shall repair any damage or
injury to the Premises caused thereby, and if not so removed by Tenant then
Landlord may have same so removed at Tenant's expense.

     20. ATTORNEY'S FEES:  In case suit should be brought for the possession of
the Premises, for the recovery of any sum due hereunder, or because of the
breach of any other covenant herein, the losing party shall pay to the
prevailing party a reasonable attorney's fee as part of its costs which shall be
deemed to have accrued on the commencement of such action.

     21. TENANT'S DEFAULT:  The occurrence of any of the following shall
constitute a material default and breach of this Lease by Tenant:  a) Any
failure by Tenant to pay the rental or to make any other payment required to be
made by Tenant hereunder provided however, that Tenant may cure such default by
payment to Landlord of the Base Monthly Rent or other sum due within ten (10)
days after receipt by Tenant of written notice specifying Landlord has failed to
receive the amount in question; b) The abandonment of the Premises by Tenant; c)
A failure by Tenant to observe and perform any other provision of this Lease to
be observed or performed by Tenant, where such failure continues for thirty (30)
days after written notice thereof by Landlord to Tenant; provided, however, that
if the nature of such default is such that the same cannot reasonably be cured
within such thirty (30) day period Tenant shall not be deemed to be in default
if Tenant shall within such period commence such cure and thereafter diligently
prosecute the same to completion; d) The making by Tenant of any general
assignment


                                          12
<PAGE>

for the benefit of creditors; the filing by or against Tenant of a petition to
have Tenant adjudged a bankrupt or of a petition for reorganization or
arrangement under any law relating to bankruptcy (unless, in the case of a
petition filed against Tenant, the same is dismissed after the filing); the
appointment of a trustee or receiver to take possession of substantially all of
Tenant's assets located at the Premises or of Tenant's interest in this Lease,
where possession is not restored to Tenant within thirty (30) days; or the
attachment, execution or other judicial seizure of substantially all of Tenant's
assets located at the Premises or of Tenant's interest in this Lease, where such
seizure is not discharged within thirty (30) days.  The notice requirements set
forth herein are in lieu of and not in addition to the notices required by
California Code of Civil Procedure Section 1161.

         A.   REMEDIES:  In the event of any such default by Tenant, then in
addition to any other remedies available to Landlord at law or in equity,
Landlord shall have the immediate option to terminate this Lease and all rights
of Tenant hereunder by giving written notice of such intention to terminate.  In
the event that Landlord shall elect to so terminate this Lease then Landlord may
recover from Tenant: a) the worth at the time of award of any unpaid rent which
had been earned at the time of such termination; plus b) the worth at the time
of award of the amount by which the unpaid rent would have been earned after
termination until the time of award exceeds the amount of such rental loss
Tenant proves could have been reasonably avoided; plus c) the worth at the time
of award of the amount by which the unpaid rent for the balance of the Lease
Term after the time of award exceeds the amount of such rental loss that Tenant
proves could be reasonably avoided; plus d) any other amount necessary to
compensate Landlord for all the detriment directly and foreseeably caused by
Tenant's failure to perform his obligations under this Lease or which in the
ordinary course of things would be likely to result therefrom, and e) at
Landlord's election, such other amounts in addition to or in lieu of the
foregoing as may be permitted from time to time by applicable California law.
The term "rent", as used herein, shall be deemed to be and to mean the minimum
monthly installments of Base Monthly Rent and all other sums required to be paid
by Tenant pursuant to the terms of this Lease, all other such sums being deemed
to be additional rent due hereunder.  As used in (a) and (b) above, the "worth
at the time of award" to be computed by allowing interest at the rate of the
discount rate of the Federal Reserve Bank of San Francisco plus five (5%)
percent per annum.  As used in (c) above, the "worth at the time of award" to be
computed by discounting such amount at the discount rate of the Federal Reserve
Bank of San Francisco at the time of award plus one (1%) percent.

         B.   RIGHT TO RE-ENTER:  In the event of any such default by Tenant,
Landlord shall also have the right, with or without terminating this Lease, to
re-enter the Premises and remove all persons and property from the Premises;
such property may be removed and stored in a public warehouse or elsewhere at
the cost of and for the account of Tenant and disposed of by Landlord in any
manner permitted by law.


                                          13
<PAGE>

         C.   ABANDONMENT:  In the event of the abandonment of the Premises by
Tenant or in the event that Landlord shall elect to re-enter as provided in
paragraph 21(B) above or shall take possession of the Premises pursuant to legal
proceeding or pursuant to any notice provided by law, then if Landlord does not
elect to terminate this Lease as provided in paragraph 21(A) above, then the
provisions of California Civil Code Section 1951.4, as amended from time to
time, shall apply and Landlord may from time to time, without terminating this
Lease, either recover all rental as it becomes due or relet the Premises or any
part thereof for such term or terms and at such rental or rentals and upon such
other terms and conditions as Landlord in its sole discretion may deem advisable
with the right to make alterations and repairs to the Premises.  In the event
that Landlord shall elect to so relet, then rentals received by Landlord from
such reletting shall be applied: first, to the payment of any indebtedness other
than Base Monthly Rent due hereunder from Tenant to Landlord; second, to the
payment of any cost of such reletting; third, to the payment of the cost of any
reasonable alterations and repairs to the Premises; fourth, to the payment of
Base Monthly Rent due and unpaid hereunder; and the residue, if any, shall be
held by Landlord and applied in payment of future Base Monthly Rent as the same
may become due and payable hereunder.  Should that portion of such rentals
received from such reletting during any month, which is applied by the payment
of rent hereunder, be less than the rent payable during that month by Tenant
hereunder, then Tenant shall pay such deficiency to Landlord immediately upon
demand therefor by Landlord.  Such deficiency shall be calculated and paid
monthly.  Tenant shall also pay to Landlord, as soon as ascertained, any costs
and expenses incurred by Landlord in such reletting or in making such
alterations and repairs not covered by the rentals received from such reletting.

         D.   NO TERMINATION:  No re-entry or taking possession of the Premises
by Landlord pursuant to 21(B) or 21(C) of this Article 22 shall be construed as
an election to terminate this Lease unless a written notice of such intention be
given to Tenant or unless the termination thereof be decreed by a court of
competent jurisdiction.  Notwithstanding any reletting without termination by
Landlord because of any default by Tenant, Landlord may at any time after such
reletting elect to terminate this Lease for any such default.

     22. SURRENDER OF LEASE:  The voluntary or other surrender of this Lease by
Tenant or a mutual cancellation thereof., shall not automatically effect a
merger of the Lease with Landlord's ownership of the Building or Premises.
Instead, at the option of Landlord, Tenant's surrender may terminate all or any
existing sublease or subtenancies, or may operate as an assignment to Landlord
of any or All such subleases or subtenancies, thereby creating a direct
Landlord-Tenant relationship between Landlord and any subtenants.


                                          14
<PAGE>

     23. HABITUAL DEFAULT:  Notwithstanding anything to the contrary contained
in paragraph 21, 21 (A) (B) (C) and (D), the parties hereto agree that if the
Tenant shall have defaulted in the performance of any (but not necessarily the
same) term or condition of this Lease for three or more times during any twelve
month period during the Lease Term hereof, then such conduct shall, at the
election of the Landlord, represent a separate event of default which cannot be
cured by the Tenant.  Tenant acknowledges that the purpose of this provision is
to prevent repetitive defaults by the Tenant under the Lease, which work a
hardship upon the Landlord, and deprive the Landlord of the timely performance
by the Tenant hereunder.

     24. LANDLORD'S DEFAULT:  In the event of Landlord's failure to perform any
of its covenants or agreements under this Lease, Tenant shall give Landlord
written notice of such failure and shall give Landlord thirty (30) days or such
other reasonable opportunity to cure or to commence to cure such failure prior
to any claim for breach or for damages resulting from such failure.  In
addition, upon any such failure by Landlord, Tenant shall give notice by
registered or certified main to any person or entity with a security interest in
the Premises ("Mortgagee") that has provided Tenant with notice of its interest
in the Premises, and shall provide such Mortgagee a reasonable opportunity to
cure such failure, including such time to obtain possession of the Premises by
power of sale or judicial foreclosure, if such should prove necessary to
effectuate a cure.  Tenant agrees that each of the Mortgagees to whom this Lease
has been assigned is an expressed third party beneficiary hereof.  Tenant shall
not make any prepayment of rent more than one (1) month in advance without the
prior written consent of such Mortgagee.  Tenant waives any right under
California Civil Code Section 1950.7 or any other present or future law to the
collection of any payment or deposit from such Mortgagee or any purchaser at a
foreclosure sale of such Mortgagee's interest unless such Mortgagee or such
purchaser shall have actually received and not refunded the applicable payment
or deposit.

     25. NOTICES:  All notices, demands, requests, or consents required to be
given under this Lease shall be sent in writing by U.S. certified mail, return
receipt requested, or by personal delivery addressed to the party to be notified
at the address for such party specified in paragraph 1 of this Lease, or to such
other place as the party to be notified may from time to time designate by at
least fifteen (15) days prior notice to the notifying party.

     26. ENTRY BY LANDLORD:  Tenant shall permit Landlord and his agents to
enter into and upon said Premises at all reasonable times subject to any
security regulations of Tenant for the purpose of inspecting the same or for the
purpose of maintaining the Premises or for the purpose of making repairs,
alterations or additions to any other portion of said Premises or for the
purpose of erecting additional building(s) and improvements on the land where
the Premises are situated, or on adjacent land owned



                                          15
<PAGE>

by Landlord, including the erection and maintenance of such scaffolding,
canopies, fences and props as may be required without any abatement or reduction
of Base Monthly Rent or without any liability to Tenant for any loss of
occupation or quiet enjoyment of the Premises thereby occasioned; and Tenant
shall permit Landlord and his agents, at any time within one hundred eighty
(180) days prior to the Expiration Date (or at any time during the Lease if
Tenant is in default hereunder), to place upon the Premises any "For Sale" or
"For Lease" signs and exhibit the Premises to real estate brokers and
prospective tenants at reasonable hours.  Landlord shall comply with Tenant's
security procedures applicable to the Premises and shall not unreasonably
interfere with Tenant's use of the Premises.

     27. DESTRUCTION OF PREMISES:

         A.   DESTRUCTION BY AN INSURED CASUALTY:  In the event of a partial
destruction of the Premises by a casualty for which Landlord has received
insurance proceeds sufficient to repair the damage or destruction during the
Lease Term from any cause, Landlord shall forthwith repair the same, provided
such repairs can be made within one hundred eighty (180) days from the date of
receipt of all necessary governmental approvals necessary under the laws and
regulations of State, Federal, County or Municipal authorities, such partial
destruction shall in no way annul or void this Lease, except that Tenant shall
be entitled to a proportionate reduction of Base Monthly Rent while such repairs
are being made, such proportionate reduction to be based upon the extent to
which the making of such repairs shall interfere with the business carried on by
Tenant in the Premises.  For purposes of this paragraph "partial destructive"
shall mean destruction of no greater than one-third (1/3) of the replacement
cost of the Premises, including the replacement cost of the Tenant Improvements
paid for by Landlord.  In the event the Premises are more than partially
destroyed, or in the event the repairs cannot be made in one hundred eighty
(180) days, Landlord or Tenant may elect to terminate this Lease.  Landlord
shall not be required to restore Alterations or replace Tenant's fixtures or
personal property.  In respect to any partial destruction which Landlord is
obligated to repair or may elect to repair under the terms of this paragraph,
the provision of Section 1932, Subdivision 2, and of Section 1933, Subdivision
4, of the Civil Code of the State of California and any other similarly enacted
statue are waived by Tenant and the provisions of this paragraph 28 shall govern
in the case of such destruction.

         B.   DESTRUCTION BY AN UNINSURED CASUALTY:  In the event of a total or
partial destruction of the Premises by an uninsured casualty, the Lease shall
automatically terminate, unless Landlord elects to rebuild.  In the event of a
destruction by an uninsured casualty (i) of greater than one-third (1/3) of the
replacement cost of the Premises, or (ii) that can not be repaired within one
hundred eighty (180) days, Tenant may elect to terminate this Lease.


                                          16
<PAGE>

     28. ASSIGNMENT OR SUBLEASE:

         A.   CONSENT BY LANDLORD:  In the event Tenant desires to assign this
Lease or any interest therein including, without limitation, a pledge, mortgage
or other hypothecation, or sublet the Premises or any part thereof, Tenant shall
deliver to Landlord substantially complete forms of any such agreement and of
all ancillary agreements with the proposed assignee or subtenant, financial
statements, and any additional information as reasonably required to determine
whether it will consent to the proposed assignment or sublease.  The notice
shall give the name and current address of the proposed assignee/subtenant,
proposed use of the Premises, rental rate and current financial statement, and
upon request to Tenant, Landlord shall be given additional information as
reasonably required to determine whether it will consent to the proposed
assignment or sublease.  Landlord shall then have a period of ten (10) days
following receipt of such notice within which to notify Tenant in writing that
Landlord elects (i) to terminate this Lease as to the space so affected as of
the date so specified by Tenant in which event Tenant will be relieved of all
further obligations hereunder as to such space (in which case Landlord shall be
responsible for the payment of any real estate commissions due), (ii) to permit
Tenant to assign or sublet such space to the named assignee/subtenant on the
terms and conditions set forth in the notice, or (iii) to refuse consent.  If
Landlord should fail to notify Tenant in writing of such election within said
ten (10) day period, Landlord shall be deemed to have elected option (ii) above.
If Landlord exercises its option to terminate this Lease in part in the event
Tenant desires to sublet or assign part of the Premises, then (i) this Lease
shall end and expire, with respect to such part of the Premises, on the date
upon which the proposed sublease was to commence, and (ii) from and after such
date, the Base Monthly Rent and Tenant's allocable share of all other costs and
charges shall be adjusted, based upon the proportion that the rentable area of
the Premises remaining bears to the total rentable area of the Premises.  If
Landlord does not exercise its option to terminate this Lease, Landlord's
consent (which must be in writing and in form reasonably satisfactory to
Landlord) to the proposed assignment or sublease shall not be unreasonably
withheld or delayed, provided and upon condition that: (i) The proposed assignee
or subtenant is engaged in a business that is limited to the use expressly
permitted under this Lease; (ii) The proposed sublease shall be in form
reasonably satisfactory to Landlord; (iii) Tenant shall reimburse Landlord on
demand for any costs that may be incurred by Landlord in connection with said
assignment or sublease, including the costs of making investigations as to the
acceptability of the proposed assignee or subtenant and legal costs incurred in
connection with the granting of any requested consent; and (iv) Tenant shall not
have advertised or publicized in any way the availability of the Premises
without prior notice to Landlord.

Notwithstanding the provisions of this paragraph 28, Tenant may, without
Landlord's prior written consent and without Landlord's participation in
subleasing profits, sublet the Premises or assign the Lease to: (i) a
subsidiary, affiliate, division or corporation


                                          17
<PAGE>

controlled or under common control with Tenant; (ii) a successor corporation
related to Tenant by merger, consolidation, non-bankruptcy reorganization, or
government action; or (iii) a purchaser of substantially all of Tenant's assets.
For the purpose of this Lease, sale of Tenant's capital stock through any public
exchange shall not be deemed an assignment, subletting, or any other transfer of
the Lease or the Premises.

         B.   ASSIGNMENT OR SUBLETTING CONSIDERATION:  Any rent or other
economic consideration realized by Tenant under any such sublease and assignment
in excess of the rent payable hereunder (including an allocation of the purchase
price attributable to Tenant's leasehold interest in the event of a sale of the
Tenant's business), after the net unamortized cost of the Tenant Improvements
for which Tenant has itself paid, and reasonable subletting and assignment
costs, shall be divided and paid sixty-seven percent (67%) to Landlord and
thirty-three percent (33%) to Tenant.  Tenant's obligation to pay over
Landlord's portion of the consideration shall constitute an obligation for
additional rent hereunder.  The above provisions relating to Landlord's right to
terminate the Lease and relating to the allocation of bonus rent are
independently negotiated terms of the Lease, constitute a material inducement
for the Landlord to enter into the Lease, and are agreed as between the parties
to be commercially reasonable.  No assignment or subletting by Tenant shall
relieve Tenant of any obligation under this Lease.  Any assignment or subletting
which conflicts with the provisions hereof shall be void.

         C.   NO RELEASE:  Any assignment or sublease shall be made only if and
shall not be effective until the assignee or subtenant shall execute,
acknowledge and deliver to Landlord an agreement, in form and substance
satisfactory to Landlord, whereby the assignee or subtenant shall assume all of
the obligations of this Lease on the part of Tenant to be performed or observed
and shall be subject to all of the covenants, agreements, terms, provisions and
conditions contained in this Lease.  Notwithstanding any such sublease or
assignment and the acceptance of rent or additional rent by Landlord from any
subtenant or assignee, Tenant or any guarantor shall and will remain fully
liable for the payment of the rent and additional rent due, and to become due
hereunder, for the performance of all of the covenants, agreements, terms,
provisions and conditions contained in this Lease on the part of Tenant to be
performed and for all acts and omissions of any licensee, subtenant, assignee or
any other person claiming under or through any subtenant that shall be in
violation of any of the terms and conditions of this Lease, and any such
violation shall be deemed to be a violation by Tenant.  Tenant shall further
indemnify, defend and hold Landlord harmless from and against any and all
losses, liabilities, damages, costs and expenses (including reasonable attorney
fees) resulting from any claims that may be made against Landlord by the
proposed assignee or subtenant or by any real estate brokers or other persons
claiming a commission or similar compensation in connection with the proposed
assignment or sublease.


                                          18
<PAGE>

         D.   EFFECT OF DEFAULT:  In the event of Tenant's default, Tenant
hereby assigns all rents due from any assignment or subletting to Landlord as
security for performance of its obligations under this Lease and Landlord may
collect such rents as Tenant's Attorney-in-Fact, except that Tenant may collect
such rents unless a default occurs as described in paragraph 21 above.  The
termination of this Lease due to Tenant's default shall not automatically
terminate any assignment or sublease then in existence.  At the election of
Landlord, the assignee or subtenant shall attorn to Landlord and Landlord shall
undertake the obligations of the Tenant under the sublease or assignment;
provided the Landlord shall not be liable for prepaid rent, security deposits or
other defaults of the Tenant to the subtenant or assignee, or any acts or
omissions of Tenant, its agents, employees or invitees.

     29. CONDEMNATION:  If any part of the Premises shall be taken for any
public or quasipublic use, under any statute or by right of eminent domain or
private purchase in lieu thereof, and a part thereof remains which is
susceptible of occupation hereunder, this Lease shall as to the part so taken,
terminate as of the date title shall vest in the condemnor or purchaser, and the
Base Monthly Rent payable hereunder shall be adjusted so that the Tenant shall
be required to pay for the remainder of the Lease Term only such portion of such
rent as the value of the part remaining after such taking bears to the value of
the entire Premises prior to such taking but in such event Landlord shall have
the option to terminate this Lease as of the date when title to the part so
taken vests in the condemnor or purchaser. If all of the Premises, or such part
thereof be taken so that there does not remain a portion susceptible for
occupation hereunder, this Lease shall thereupon terminate.  If a part or all of
the Premises be taken, all compensation awarded upon such taking shall go to the
Landlord and the Tenant shall have no claim thereto but Landlord shall cooperate
with Tenant to recover compensation for damage to or taking of any Alterations
or for Tenant's moving costs.  Tenant hereby waives the provisions of California
Code of Civil Procedures Section 1265.130 and any other similarly enacted statue
are waived by Tenant and the provisions of this paragraph 30 shall govern in the
case of such destruction.

     30. EFFECTS OF CONVEYANCE:  The term Landlord as used in this Lease, means
only the owner for the time being of the land and Building, containing the
Premises, so that, in the event of any sale or other conveyance of said land or
Building, or in the event of a master Lease of the Building, the Landlord shall
be and hereby is entirely freed and relieved of all covenants and obligations of
the Landlord hereunder, and it shall be deemed and construed, without further
agreement between the parties and the purchaser at any such sale, or the master
tenant of the Building, that the purchaser or master tenant of the Building has
assumed and agreed to carry out any and all covenants and obligations of the
Landlord hereunder.  Landlord shall transfer and deliver Tenant's security
deposit, to the purchaser at any such sale or the master tenant of the Building,


                                          19
<PAGE>

and thereupon the Landlord shall be discharged from any further liability in
reference thereto.

     31. SUBORDINATION:  In the event Landlord notifies Tenant in writing, this
Lease shall be subordinate to any ground Lease, deed of trust, or other
hypothecation for security now or hereafter placed upon the real property of
which the Premises are a part and to any and all advances made on the security
thereof and to renewals, modifications, replacements and extensions thereof.
Tenant agrees to promptly execute and deliver any documents which may be
required to effectuate such subordination.  Notwithstanding such subordination,
Tenant's right to quiet possession of the Premises shall not be disturbed if
Tenant is not in default and so long as Tenant shall pay the rent and observe
and perform all of the provisions of this Lease.  At the request of any lender,
Tenant agrees to execute and deliver any reasonable modifications of this Lease
which do not materially adversely affect Tenant's rights hereunder.

     32. WAIVER:  The waiver by Landlord of any breach of any term, covenant or
condition, herein contained shall not be deemed to be a waiver of such term,
covenant or condition or any subsequent breach of the same or any other term,
covenant or condition herein contained.  The subsequent acceptance of rent
hereunder by Landlord shall not be deemed to be a waiver of any preceding breach
by Tenant of any term, covenant or condition of this Lease, other than the
failure of Tenant to pay the particular rental so accepted, regardless of
Landlord's knowledge of such preceding breach at the time of acceptance of such
rent.  No delay or omission in the exercise of any right or remedy by Landlord
shall impair such right or remedy or be construed as a waiver thereof by
Landlord.  No act or conduct of Landlord, including, without limitation, the
acceptance of keys to the Premises shall constitute acceptance of the surrender
of the Premises by Tenant before the Expiration Date.  Landlord's consent to or
approval of any act by Tenant which require Landlord's consent or approvals
shall not be deemed to waive or render unnecessary Landlord's consent to or
approval of any subsequent act by Tenant.

     33. HOLDING OVER.  Any holding over after the termination or Expiration
Date, shall be construed to be a tenancy from month to month terminable on
thirty (30) days written notice from either party and Tenant shall pay Base
Monthly Rent to Landlord at a rate equal to the greater of (i) one hundred fifty
percent (150%) of the Base Monthly Rent due in the month preceding the
termination or Expiration Date or (ii) one hundred fifty percent (150%) of the
Fair Market Rental (as defined in paragraph 36).  Any holding over shall
otherwise be on the terms and conditions herein specified, except those
provisions relating to the Lease Term and any options to extend or renew, which
provisions shall be of no further force and effect following the expiration of
the applicable exercise period.  Tenant shall indemnify, defend, and hold
Landlord harmless from all loss or liability (including, without limitation, any
loss or liability resulted from


                                          20
<PAGE>

any claim against Landlord made by any succeeding tenant) founded on or
resulting from Tenant's failure to surrender the Premises and losses to Landlord
due to lost opportunities to lease the Premises to succeeding tenants.

     34. SUCCESSORS AND ASSIGNS:  The covenants and conditions herein contained
shall, subject to the provisions of paragraph 27, apply to and bind the heirs,
successors, executors, administrators and assigns of all the parties hereto; and
all of the parties hereto shall be jointly and severally liable hereunder.

     35. ESTOPPEL CERTIFICATES:  Tenant shall at any time during the Lease
Term, within ten (10) business days following written notice from Landlord,
execute and deliver to Landlord a statement in writing certifying that this
Lease is unmodified and in full force and effect (or, if modified, stating the
nature of such modification) and the date to which the rent and other charges
are paid in advance, if any, and acknowledging that there are not, to Tenant's
knowledge, any uncured defaults on the part of Landlord hereunder or specifying
such defaults if they are claimed.  Any such statement may be conclusively
relied upon by any prospective purchaser or encumbrancer of the Premises.
Tenant's failure to deliver such statement within such time shall be conclusive
upon the Tenant that: (i) this Lease is in full force and effect, without
modification except as may be represented by Landlord; (ii) there are not
uncured defaults in Landlord's performance.  Tenant also agrees to provide the
most current three (3) years of audited financial statements within ten (10)
business days of a request by Landlord for Landlord's use in financing the
Premises with commercial lenders.

     36. OPTION TO EXTEND THE LEASE TERM:

         A.   GRANT AND EXERCISE OF OPTION:  Landlord hereby grants to Tenant,
upon and subject to the terms and conditions set forth in this paragraph, the
option (the "Option") to extend the Lease Term for an additional term (the
"Option Term"), which Option Term shall be a period of thirty-six (36) months.
The Option Term shall be exercised, if at all, by written notice to Landlord on
or before the date that is nine (9) months prior to the Expiration Date. if
Tenant exercises the Option, each of the terms, covenants and conditions of this
Lease except this paragraph shall apply during the Option Term as though the
expiration date of the Option Term was the date originally set forth herein as
the Expiration Date, provided that the Base Monthly Rent to be paid shall be the
greater of (i) the Base Monthly Rent applicable to the period immediately prior
to the commencement of the Option Term, or (ii) the Fair Market Rental, as
hereinafter defined, for the Premises for the Option Term.  Anything contained
herein to the contrary notwithstanding, if Tenant is in monetary or material
non-monetary default under any of the terms, covenants or conditions of this
Lease either at the time Tenant exercises the Option or at any time thereafter
prior to the commencement date of the Option Term, Landlord shall have, in
addition to all of Landlord's other rights and remedies provided in


                                          21
<PAGE>

this Lease, the right to terminate the Option upon notice to Tenant, in which
event the expiration date of this Lease shall be and remain the Expiration Date.
As used herein, the term "Fair Market Rental" for the Premises shall mean the
rental and all other monetary payments including any escalations and adjustments
thereto (including without limitation Consumer Price Indexing) there being
obtained for new leases of space comparable in age and quality to the Premises
in the locality of the Building that Landlord could obtain during the Option
Term from a third party desiring to lease the Premises for the Option Term.
Fair Market Rental shall further take into account that (i) that Tenant is in
occupancy of the Premises and making functional use of the space in its then
existing condition, and (ii) that no brokerage commission is payable.

         B.   DETERMINATION OF FAIR MARKET RENTAL:  If Tenant exercises the
Option, Landlord shall send to Tenant a notice setting forth the Fair Market
Rental for the Premises for the Option Term, on or before the date that is one
hundred fifty (150) days prior to the Expiration Date.  If Tenant disputes
Landlord's determination of the Fair Market Rental for the Option Term, Tenant
shall, within thirty (30) days after the date of Landlord's notice setting forth
the Fair Market Rental for the Option Term, send to Landlord a notice stating
that Tenant either (i) elects to terminate its exercise of the Option, in which
event the Option shall lapse and this Lease shall terminate on the Expiration
Date, or (ii) disagrees with Landlord's determination of Fair Market Rental for
the Option Term and elects to resolve the disagreement as provided in paragraph
36(C) below.  If Tenant does not send to Landlord a notice as provided in the
previous sentence, Landlord's determination of the Fair Market Rental shall be
the basis for determining the Base Monthly Rent to be paid by Tenant hereunder
during the Option Term.  If Tenant elects to resolve the disagreement as
provided in paragraph 36(C) below and such procedures shall not have been
concluded prior to the commencement date of the Option Term, Tenant shall pay
Base Monthly Rent to Landlord hereunder adjusted to reflect the Fair Market
Rental as determined by Landlord in the manner provided above. if the amount of
Fair Market Rental as finally determined pursuant to in paragraph 36(C) below is
greater than Landlord's determination, Tenant shall pay to Landlord the
difference between the amount paid by Tenant and the Fair Market Rental as so
determined in paragraph 36(C) below within thirty (30) days after the
determination if the Fair Market Rental as finally determined in paragraph 36(C)
below is less than Landlord's determination, the difference between the amount
paid by Tenant and the Fair Market Rental as so determined in paragraph 36(C)
below shall be credited against the next installments of rent due from Tenant to
Landlord hereunder.

         C.   RESOLUTION OF A DISAGREEMENT OVER THE FAIR MARKET RENTAL:  Any
disagreement regarding the Fair Market Rental shall be resolved as follows:

              1.   Within thirty (30) days after Tenant's response to 
Landlord's notice to Tenant of the Fair Market Rental, Landlord and Tenant 
shall meet no less than

                                          22
<PAGE>

two (2) times, at a mutually agreeable time and place, to attempt to resolve any
such disagreement.

              2.    If within the thirty (30) day period referred to in (i) 
above, Landlord and Tenant can not reach agreement as to the Fair Market 
Rental, they shall each select one appraiser to determine the Fair Market 
Rental.  Each such appraiser shall arrive at a determination of the Fair 
Market Rental and submit their conclusions to Landlord and Tenant within 
thirty (30) days after the expiration of the thirty (30) day consultation 
period described in (i) above.

              3.    If only one appraisal is submitted within the requisite 
time period, it shall be deemed to be the Fair Market Rental.  If both 
appraisals are submitted within such time period, and if the two appraisals 
so submitted differ by less than ten percent (10%) of the higher of the two, 
the average of the two shall be the Fair Market Rental.  If the two 
appraisals differ by more than ten percent (10%) of the higher of the two, 
then the two appraisers shall immediately select a third appraiser who shall 
within thirty (30) days after his or her selection make a determination of 
the Fair Market Rental and submit such determination to Landlord and Tenant.  
This third appraisal will then be averaged with the closer of the two 
previous appraisals and the result shall be the Fair Market Rental.

              4.    All appraisers specified pursuant to this paragraph shall 
be members of the American Institute of Real Estate Appraisers with not less 
than ten (10) years experience appraising office and industrial properties in 
the Santa Clara Valley.  Each party shall pay the cost of the appraiser 
selected by such party and one-half of the cost of the third appraiser plus 
one-half of any other costs incurred in resolving the dispute pursuant to 
this paragraph.

     37. OPTIONS:  All Options provided Tenant in this Lease are personal and
granted to original Tenant or its affiliates and are not exercisable by any
third party should Tenant assign or sublet all or a portion of its rights under
this Lease, unless Landlord consents to permit exercise of any option by any
assignee or subtenant, in Landlord's sole discretion.  In the event that Tenant
hereunder has any multiple options to extend this Lease, a later option to
extend the Lease cannot be exercised unless the prior option has been so
exercised.

     38. QUIET ENJOYMENT:  Upon Tenant's faithful and timely performance of all
the terms and covenants of the Lease, Tenant shall quietly have and hold the
Premises for the Lease Term and any extensions thereof.

     39. BROKERS:  Tenant represents it has not utilized or contacted a real
estate broker or finder with respect to this Lease and Tenant agrees to
indemnify and hold


                                          23
<PAGE>

Landlord harmless against any claim, cost, liability or cause of action asserted
by any broker or finder claiming through Tenant.

     40. This section intentionally left blank.

     41. AUTHORITY OF PARTIES:  Each individual executing this Lease on behalf
of Tenant represents and warrants that he is duly authorized to execute and
deliver this Lease on behalf of the corporation, in accordance with a duly
adopted resolution of the Board of Directors of said corporation or in
accordance with the by-laws of said corporation, and that this Lease is binding
upon said corporation in accordance with its terms.  Each individual executing
this Lease on behalf of Landlord represents and warrants that he is duly
authorized to execute and deliver this Lease on behalf of the limited
partnership and that this Lease is binding upon said limited partnership in
accordance with its terms.

     42. MISCELLANEOUS PROVISIONS:

         A.   RENT:  All monetary sums due from Tenant to Landlord under this
Lease shall be deemed to be rent.

         B.   MANAGEMENT FEE:  All maintenance and utility services
administered by Landlord and subject to reimbursement by Tenant shall include a
property management fee to Landlord of fifteen percent (15%).

         C.   PERFORMANCE BY LANDLORD:  If Tenant fails to perform any
obligation required under this Lease or by law or governmental regulation,
Landlord in its sole discretion may without notice perform such obligation, in
which event Tenant shall pay Landlord as additional rent all sums paid by
Landlord in connection with such substitute performance within ten (10) days
following Landlord's written notice for such payment.

         D.   INTEREST:  All sums due hereunder, including rent and additional
rent, if not paid when due shall bear interest at the maximum rate permitted
under California law accruing from the date due until the date paid to Landlord.

         E.   RIGHTS AND REMEDIES:  All rights and remedies hereunder are
cumulative and not alternative to the extent permitted by law and are in
addition to all other rights and remedies in law and in equity.

         F.   SURVIVAL OF INDEMNITIES:  All indemnification, defense, and hold
harmless obligations of Landlord and Tenant under the Lease shall survive the
expiration or sooner termination of the Lease.


                                          24
<PAGE>

         G.   SEVERABILITY:  If any term or provision of this Lease is held
unenforceable or invalid by a court of competent jurisdiction, the remainder of
the Lease shall not be invalidated thereby but shall be enforceable in
accordance with its terms, omitting the invalid or unenforceable term.

         H.   CHOICE OF LAW:  This Lease shall be governed by and construed in
accordance with California law.

         I.   TIME:  Time is of the essence hereunder.

         J.   ENTIRE AGREEMENT:  This instrument contains all of the agreements
and conditions made between the parties hereto and may not be modified orally or
in any other manner than by an agreement in writing signed by all of the parties
hereto or their respective successors in interest.

         K.   REPRESENTATIONS:  Tenant acknowledges that neither Landlord or
its affiliates or agents have made any agreements, representations, warranties
or promises with respect to the demised Premises or the Building of which they
are a part, or with respect to present or future rents, expenses, operations,
tenancies or any other matter.  Except as herein expressly set forth herein,
Tenant relied on no statement of Landlord or its agents for that purpose.

         L.   HEADINGS:  The headings or titles to the paragraphs of this Lease
are not a part of this Lease and shall have no effect upon the construction or
interpretation of any part thereof.

IN WITNESS WHEREOF, Landlord and Tenant have executed these presents, the day
and year first above written.


LANDLORD:  Sobrato Interests,               TENANT:  Affymetrix, Inc.
a California limited Partnership            a California corporation

By:                                         By:
   --------------------------------            --------------------------------
Its:                                        Its:
    -------------------------------             -------------------------------

<PAGE>
                                                                    EXHIBIT 23.2
 
                   CONSENT OF TOWNSEND AND TOWNSEND AND CREW
 
    This will confirm our consent to the reference to our firm under the caption
"Experts" in the Registration Statement (Form S-3) and related Prospectus of
Affymetrix, Inc. for the registration of 1,500,000 shares of its common stock.
 
                                          TOWNSEND and TOWNSEND and CREW LLP
 
                                          /s/ DANIEL J. FURNISS
 
                                          Daniel J. Furniss
 
                                          Partner
 
Palo Alto, California
 
Friday, October 17, 1997

<PAGE>
                                                                    EXHIBIT 23.3
 
               CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS
 
    We consent to the reference to our firm under the caption "Experts" and to
the use of our report dated January 23, 1997 in the Registration Statement (Form
S-3) and related Prospectus of Affymetrix, Inc. for the registration of
1,725,000 shares of its common stock.
 
                                                               ERNST & YOUNG LLP
 
Palo Alto, California
October 17, 1997


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