AFFYMETRIX INC
S-1/A, 1996-06-03
COMMERCIAL PHYSICAL & BIOLOGICAL RESEARCH
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<PAGE>
   
      AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JUNE 3, 1996
    
 
                                                       REGISTRATION NO. 333-3648
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                            ------------------------
 
   
                                AMENDMENT NO. 3
                                       TO
                                    FORM S-1
                             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) 522-6000
 
         (Address, Including Zip Code, and Telephone Number, Including
            Area Code, of Registrant's Principal Executive Offices)
 
  KENNETH J. NUSSBACHER, EXECUTIVE VICE PRESIDENT AND CHIEF FINANCIAL OFFICER
     3380 CENTRAL EXPRESSWAY, SANTA CLARA, CALIFORNIA 95051; (408) 522-6000
 
       (Name, Address Including Zip Code, and Telephone Number, Including
                        Area Code, of Agent For Service)
                            ------------------------
 
                                   COPIES TO:
 
<TABLE>
<S>                                       <C>
           Julian N. Stern                            Alan K. Austin
          August J. Moretti                         Elizabeth R. Flint
         Stephen C. Ferruolo                        Elizabeth M. Kurr
   Heller Ehrman White & McAuliffe          Wilson, Sonsini, Goodrich & Rosati
        525 University Avenue                       650 Page Mill Road
     Palo Alto, California 94301               Palo Alto, California 94304
            (415) 324-7000                            (415) 493-9300
</TABLE>
 
                            ------------------------
 
        APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:
    AS SOON AS PRACTICABLE FOLLOWING THE EFFECTIVENESS OF THIS REGISTRATION
                                   STATEMENT.
 
    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, 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,  check the following box  and
list  the Securities Act registration statement  number of the earlier effective
registration statement for the same offering. / /
 
    If this Form  is a post-effective  amendment filed pursuant  to Rule  462(c)
under  the Securities Act, check  the following box and  list the Securities Act
registration 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
                                                              PROPOSED          MAXIMUM
                                                               MAXIMUM         AGGREGATE        AMOUNT OF
         TITLE OF EACH CLASS OF            AMOUNT TO BE    OFFERING PRICE      OFFERING       REGISTRATION
      SECURITIES TO BE REGISTERED         REGISTERED (1)    PER SHARE (2)      PRICE (2)         FEE (2)
<S>                                       <C>              <C>              <C>              <C>
              COMMON STOCK                   6,900,000         $13.00         $89,700,000      $30,932(3)
</TABLE>
    
 
   
(1) Includes 900,000 shares which the Underwriters will be granted the option to
    purchase to cover over-allotments.
    
 
   
(2)  Estimated  solely  for  the purpose  of  calculating  the  registration fee
    pursuant to Rule 457 under the Securities Act of 1933.
    
 
   
(3) Of this amount, $25,776 was previously paid.
    
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>
                                AFFYMETRIX, INC.
                             CROSS-REFERENCE SHEET
 
<TABLE>
<CAPTION>
                        ITEM AND HEADING
           FOR S-1 REGISTRATION STATEMENT PROSPECTUS                             LOCATION IN PROSPECTUS
- ----------------------------------------------------------------  -----------------------------------------------------
<C>        <S>                                                    <C>
       1.  Forepart of the Registration Statement and Outside
            Front Cover Page of Prospectus......................  Outside Front Cover Page; Additional Information
       2.  Inside Front and Outside Back Cover Pages of
            Prospectus..........................................  Inside Front Cover Page
       3.  Summary Information, Risk Factors and Ratio of
            Earnings to Fixed Charges...........................  Summary; Risk Factors
       4.  Use of Proceeds......................................  Summary; Use of Proceeds
       5.  Determination of Offering Price......................  Outside Front Cover Page; Underwriting
       6.  Dilution.............................................  Dilution
       7.  Selling Security Holders.............................  Not Applicable
       8.  Plan of Distribution.................................  Outside and Inside Front Cover Pages; Underwriting
       9.  Description of Securities to be Registered...........  Summary; Capitalization; Description of Capital Stock
      10.  Interests of Named Experts and Counsel...............  Legal Matters; Experts
      11.  Information with Respect to the Registrant...........  Outside and Inside Front Cover Pages; Summary; Risk
                                                                   Factors; Use of Proceeds; Dividend Policy;
                                                                   Capitalization; Dilution; Selected Financial Data;
                                                                   Management's Discussion and Analysis of Financial
                                                                   Condition and Results of Operations; Business;
                                                                   Management; Certain Transactions; Principal
                                                                   Shareholders; Description of Capital Stock; Shares
                                                                   Eligible for Future Sale; Financial Statements
      12.  Disclosure of Commission Position on Indemnification
            for Securities Act Liabilities......................  Not Applicable
</TABLE>
<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 JUNE 3, 1996
    
 
                                      LOGO
 
   
                                6,000,000 SHARES
    
 
                                  COMMON STOCK
 
   
    All of the 6,000,000 shares of Common Stock offered hereby are being sold by
Affymetrix, Inc. ("Affymetrix" or the "Company"). Prior to this offering,  there
has  been no public market for the Common  Stock of the Company. It is currently
estimated that the  initial public  offering price  will be  between $11.00  and
$13.00  per share. See "Underwriting" for  information relating to the method of
determining the initial public offering price.
    
                               ------------------
 
          THE COMMON STOCK OFFERED HEREBY INVOLVES A HIGH DEGREE OF RISK.
                    SEE "RISK FACTORS" BEGINNING ON PAGE 6.
                                ----------------
 
THESE SECURITIES  HAVE  NOT  BEEN  APPROVED OR  DISAPPROVED  BY  THE  SECURITIES
   AND  EXCHANGE  COMMISSION  OR  ANY  STATE  SECURITIES  COMMISSION  NOR HAS
     THE  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>
- ---------------------------------------------------------------------------------
- ---------------------------------------------------------------------------------
                                                   UNDERWRITING
                                    PRICE TO       DISCOUNTS AND     PROCEEDS TO
                                     PUBLIC         COMMISSIONS      COMPANY (1)
- ---------------------------------------------------------------------------------
<S>                               <C>              <C>              <C>
Per Share.....................          $                $                $
- ---------------------------------------------------------------------------------
Total (2).....................          $                $                $
- ---------------------------------------------------------------------------------
- ---------------------------------------------------------------------------------
</TABLE>
 
(1) Before deducting expenses payable by the Company estimated at $800,000.
 
   
(2) The Company has granted the Underwriters  a 30-day option to purchase up  to
    an   additional   900,000   shares   of  Common   Stock   solely   to  cover
    over-allotments, if any. See "Underwriting." If such option is exercised  in
    full, the total Price to Public, Underwriting Discounts and Commissions, and
    Proceeds to Company will be $     , $      , and $      , respectively.
    
                               ------------------
 
    The Common Stock is offered by the Underwriters as stated 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  delivery of  such shares  will be made
through the offices of Robertson, Stephens & Company LLC ("Robertson, Stephens &
Company"), San Francisco, California, on or about       , 1996.
 
ROBERTSON, STEPHENS & COMPANY
 
                                 CS FIRST BOSTON
 
                                                           MONTGOMERY SECURITIES
 
                  The date of this Prospectus is       , 1996
<PAGE>
Affymetrix GeneChip-TM- Technology Opportunities
- --------------------------------------------
 
      All genomics programs  are expected to  be research  collaborations.
      All diagnostic product opportunities are in research and development
      with  the indicated collaborators, except  for HIV, which Affymetrix
      introduced  as  a  "Research  Use  Only"  product  in  April   1996.
      Diagnostic 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.
 
- --------------------------------------------------------------------------------
IN CONNECTION  WITH THIS  OFFERING, THE  UNDERWRITERS MAY  OVER-ALLOT OR  EFFECT
TRANSACTIONS WHICH STABILIZE OR MAINTAIN THE MARKET PRICE OF THE COMMON STOCK OF
THE  COMPANY AT  A LEVEL ABOVE  THAT WHICH  MIGHT OTHERWISE PREVAIL  IN THE OPEN
MARKET. SUCH TRANSACTIONS  MAY BE  EFFECTED ON  THE NASDAQ  NATIONAL MARKET,  OR
OTHERWISE. SUCH STABILIZING, IF COMMENCED, MAY BE DISCONTINUED AT ANY TIME.
 
DURING  THIS OFFERING, CERTAIN PERSONS  AFFILIATED WITH PERSONS PARTICIPATING IN
THE DISTRIBUTION MAY ENGAGE  IN TRANSACTIONS FOR THEIR  OWN ACCOUNTS OR FOR  THE
ACCOUNTS  OF OTHERS IN THE COMMON STOCK PURSUANT TO EXEMPTIONS FROM RULES 10B-6,
10B-7, AND 10B-8 UNDER THE SECURITIES EXCHANGE ACT OF 1934.
<PAGE>
Affymetrix GeneChip Technology
- -----------------------------------------
 
                             [Depictions of genes,
                                double helix and
                           probe array in cartridge]
 
Affymetrix GeneChip probe arrays provide  the capacity to acquire, analyze,  and
manage complex genetic information.
 
Integrated GeneChip System
 
<TABLE>
<S>                            <C>                            <C>
[PICTURE]                      [PICTURE]                      [PICTURE]
 
GeneChip Fluidics Station      GeneChip Scanner               GeneChip Software
Controls hybridization of the  Quantitatively detects         Analyzes and manages genetic
test sample to the probe       hybridization of test sample   information from the scanner.
array.                         to the probe array.
</TABLE>
 
<PAGE>
              GeneChip Probe Array
             A GeneChip probe array currently contains
             from 16,000 to more than 100,000 different
             DNA probes. Each probe array is packaged
             in a catridge.
 
                                          Probe Array Image
                                        A GeneChip scanner image of an
                                        HIV probe array for sequencing the
                                        reverse transcriplase and protease
                                        genes. Each small square represents
                                        the quantitative hybridization
                                        intensity of a labeled test sample to
                                        a specific DNA probe.
 
             [PICTURE]
 
             [PICTURE]
 
              GeneChip Software
             GeneChip software translates the quantitative hybridization
             intensities into sequence information which can also be used for
             gene expression analysis and genetic mapping. The red "a" in the
             Sequences window indicates a mutation in HIV causing resistance to
             a class of HIV protease inhibitor drugs.
<PAGE>
    NO  DEALER, SALES REPRESENTATIVE OR ANY  OTHER PERSON HAS BEEN AUTHORIZED TO
GIVE ANY INFORMATION  OR TO  MAKE ANY  REPRESENTATIONS IN  CONNECTION WITH  THIS
OFFERING  OTHER THAN THOSE CONTAINED  IN THE PROSPECTUS, AND,  IF GIVEN OR MADE,
SUCH INFORMATION  OR REPRESENTATIONS  MUST NOT  BE RELIED  UPON AS  HAVING  BEEN
AUTHORIZED  BY  THE  COMPANY  OR  ANY  UNDERWRITER.  THIS  PROSPECTUS  DOES  NOT
CONSTITUTE AN  OFFER  TO  SELL, OR  A  SOLICITATION  OF AN  OFFER  TO  BUY,  ANY
SECURITIES  OTHER THAN THE REGISTERED SECURITIES TO WHICH IT RELATES OR AN OFFER
TO, OR SOLICITATION OF, ANY PERSON IN ANY JURISDICTION IN WHICH SUCH AN OFFER OR
SOLICITATION WOULD BE 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
THE DATE HEREOF.
 
    UNTIL        , 1996 (25 DAYS AFTER THE DATE OF THIS PROSPECTUS), ALL DEALERS
EFFECTING  TRANSACTIONS   IN  THE   REGISTERED   SECURITIES,  WHETHER   OR   NOT
PARTICIPATING  IN THIS  DISTRIBUTION, MAY BE  REQUIRED TO  DELIVER A PROSPECTUS.
THIS DELIVERY  REQUIREMENT IS  IN  ADDITION TO  THE  OBLIGATIONS OF  DEALERS  TO
DELIVER  A  PROSPECTUS WHEN  ACTING AS  UNDERWRITERS AND  WITH RESPECT  TO THEIR
UNSOLD ALLOTMENTS OR SUBSCRIPTIONS.
 
                               ------------------
 
                               TABLE OF CONTENTS
 
   
<TABLE>
<CAPTION>
                                                                            PAGE
                                                                            ----
<S>                                                                         <C>
Summary...................................................................    4
Risk Factors..............................................................    6
Use of Proceeds...........................................................   19
Dividend Policy...........................................................   19
Capitalization............................................................   20
Dilution..................................................................   21
Selected Financial Data...................................................   22
Management's Discussion and Analysis of Financial Condition and Results of
 Operations...............................................................   23
Business..................................................................   27
Management................................................................   49
Certain Transactions......................................................   55
Principal Shareholders....................................................   57
Description of Capital Stock..............................................   59
Shares Eligible for Future Sale...........................................   61
Underwriting..............................................................   63
Legal Matters.............................................................   64
Experts...................................................................   64
Additional Information....................................................   64
Glossary..................................................................   65
Index to Financial Statements.............................................  F-1
</TABLE>
    
 
                               ------------------
 
    The Company's  executive offices  are located  at 3380  Central  Expressway,
Santa Clara, California 95051. The Company's telephone number is (408) 522-6000.
 
    GeneChip-TM-  and Affymetrix-TM-  are trademarks of  the Company. Tradenames
and trademarks of other companies appearing in this Prospectus are the  property
of their respective holders.
 
                                       3
<PAGE>
                                    SUMMARY
 
    THE  FOLLOWING SUMMARY  IS QUALIFIED  IN ITS  ENTIRETY BY  THE MORE DETAILED
INFORMATION, INCLUDING "RISK  FACTORS", AND THE  FINANCIAL STATEMENTS AND  NOTES
THERETO,  APPEARING  ELSEWHERE  IN  THIS  PROSPECTUS.  THIS  PROSPECTUS CONTAINS
FORWARD-LOOKING STATEMENTS 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  "RISK FACTORS"  AND ELSEWHERE  IN THIS  PROSPECTUS. A  GLOSSARY OF
TECHNICAL TERMS USED IN THIS PROSPECTUS APPEARS AT PAGE 64 OF THIS PROSPECTUS.
                                  THE COMPANY
 
    Affymetrix 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 system consists of disposable DNA probe arrays containing
gene sequences on a chip, instruments to process the probe arrays, and  software
to  analyze  and manage  genetic information.  The Company  commenced commercial
sales of the GeneChip system  and an HIV probe array  for research use in  April
1996.
 
    The  Company  manufactures  its DNA  probe  arrays using  an  innovative and
proprietary process that combines photolithographic fabrication techniques  from
the  semicondutor  industry with  solid phase  DNA  synthesis to  assemble large
amounts of genetic information on a small  glass chip called a probe array.  The
Company can manufacture a number of identical DNA probe arrays on a glass wafer,
which  is then diced  into individual probe arrays.  Currently, each probe array
manufactured by the Company contains from 16,000 to more than 100,000  different
DNA probes.
 
    Genes  provide  the fundamental  basis  for understanding  human  health and
disease. Increased  knowledge  of  how  genes encode  the  functions  of  living
organisms  has generated  a worldwide effort  to identify and  sequence genes of
many organisms, including the estimated  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  sequences
are identified, it is anticipated that many years of additional research will be
required  to  understand the  specific function  of  each gene  and its  role in
disease. Affymetrix believes that the GeneChip system can play an important role
in this research and  its application in drug  discovery and the development  of
new  diagnostic  products. The  Company  intends to  commercialize  the GeneChip
system in  two  principal areas:  genomics,  or the  study  of genes  and  their
function, and diagnostics.
 
    In  genomics,  Affymetrix  intends  to  sell  custom  DNA  probe  arrays  to
pharmaceutical and biotechnology companies through collaborative agreements. The
Company would receive revenues in the form of probe array design and development
fees, and subsequently through the sale of DNA probe arrays and instruments.  In
addition,  the  Company  may  receive  milestone  payments  and  royalties  from
discoveries made  through the  use  of the  DNA  probe arrays.  Affymetrix  also
intends  to  use  the  GeneChip  technology  to  help  create  and commercialize
databases containing information  on the  function of  genes and  their role  in
disease.  There  can be  no assurance  that  the Company  will be  successful in
marketing its GeneChip system for these genomics applications.
 
    In diagnostics, Affymetrix intends  to develop DNA  probe arrays to  analyze
genetic  information from patient  samples to improve the  accuracy and speed of
diagnosis. The Company is pursuing diagnostic products and research applications
in infectious  diseases,  cancer  and  other  areas,  such  as  monitoring  drug
metabolism.  The  Company intends  to  market its  diagnostic  GeneChip products
directly  and  through  collaborative  partnerships.  Affymetrix  believes   its
GeneChip  technology can  also be  used as a  discovery tool  for new diagnostic
markers to be used in conventional immunoassays. There can be no assurance  that
the  Company  will be  successful  in marketing  its  GeneChip system  for these
diagnostic applications.
 
    The  Company's  first  application  for  the  GeneChip  system  is  to  help
researchers  identify mutations in HIV that cause resistance to antiviral drugs,
such as AZT. The Company believes  that monitoring such mutations may become  an
important  aspect  of  managing  patients  with  AIDS.  As  of  March  31, 1996,
Affymetrix had placed five prototype GeneChip systems for the HIV application in
academic research centers and pharmaceutical companies for research use.
 
    An important part of  the Company's strategy is  to work with  collaborative
partners  to expand the applications of  the Company's technology and to acquire
access to complementary  technologies and  resources such  as manufacturing  and
marketing. Affymetrix has two agreements with Genetics Institute, Inc. ("GI") to
apply  the Company's technology  to understand the function  of human genes. The
Company will design, manufacture and supply custom probe arrays for use in  GI's
drug  discovery  programs. Affymetrix  also has  a collaborative  agreement with
Hewlett-Packard Company ("HP"), whereby HP will develop advanced instruments  to
read  the  GeneChip probe  arrays. In  addition, in  collaboration with  HP, the
Company will develop and manufacture certain probe arrays to be marketed by HP.
 
    Affymetrix  began  operations  in  1991  as  a  division  of  Affymax   N.V.
("Affymax"),  was incorporated in  California in March  1992 and began operating
independently as a wholly-owned  subsidiary of Affymax in  March 1993. In  March
1995,  Glaxo plc, now Glaxo Wellcome  plc ("Glaxo"), purchased Affymax. Prior to
this offering, Glaxo indirectly  owns approximately 46% of  the Common Stock  of
Affymetrix.
                                  RISK FACTORS
 
   
    An  investment in the shares of Common  Stock offered hereby involves a high
degree of risk. The Company's GeneChip system and other potential products  will
require  significant additional development and  investment. While the Company's
initial product sales for research  use have not required regulatory  approvals,
the  Company  expects  that  such  approvals  will  be  required  for diagnostic
applications in the  future. There  can be no  assurance that  the Company  will
obtain  any required  regulatory approvals for  the GeneChip system  or that the
GeneChip system will be successfully commercialized or obtain market acceptance.
Other  risk  factors   include  the  Company's   early  stage  of   development,
uncertainties  relating  to  technological  approaches,  history  of  losses and
expectation of future losses,  intense competition, rapid technological  change,
limited  manufacturing  capability and  sales and  marketing experience  and the
Company's dependence on proprietary technology. See "Risk Factors."
    
 
                                       4
<PAGE>
                                  THE OFFERING
 
   
<TABLE>
<S>                                             <C>
Common Stock Offered by the Company...........  6,000,000 shares
Common Stock Outstanding after the Offering...  22,239,231 shares (1)
Use of Proceeds...............................  For  research  and   development  (including   product
                                                development  and core  research), capital expenditures
                                                (manufacturing  scale-up,  facilities  and  laboratory
                                                equipment),  expansion of sales and marketing, working
                                                capital and other general corporate purposes. See "Use
                                                of Proceeds."
Proposed Nasdaq National Market Symbol........  AFFX
</TABLE>
    
 
                             SUMMARY FINANCIAL DATA
                     (in thousands, except per share data)
 
<TABLE>
<CAPTION>
                                                                                                   THREE MONTHS ENDED
                                                              YEAR ENDED DECEMBER 31,                  MARCH 31,
                                                    --------------------------------------------  --------------------
                                                     1991     1992     1993     1994      1995      1995       1996
                                                    -------  -------  -------  -------  --------  ---------  ---------
<S>                                                 <C>      <C>      <C>      <C>      <C>       <C>        <C>
STATEMENT OF OPERATIONS DATA:
Contract and grant revenue........................  $ --     $    43  $ 1,413  $ 1,574  $  4,625  $     854  $   1,416
Operating expenses:
    Research and development......................    1,576    4,106    6,566    9,483    12,420      2,274      4,177
    General and administrative....................      261      582      577    2,303     3,833        777      1,649
                                                    -------  -------  -------  -------  --------  ---------  ---------
      Total operating expenses....................    1,837    4,688    7,143   11,786    16,253      3,051      5,826
                                                    -------  -------  -------  -------  --------  ---------  ---------
Loss from operations..............................   (1,837)  (4,645)  (5,730) (10,212)  (11,628)    (2,197)    (4,410)
Interest income (expense), net....................    --         (15)     138      532       881         23        489
                                                    -------  -------  -------  -------  --------  ---------  ---------
Net loss..........................................  $(1,837) $(4,660) $(5,592) $(9,680) $(10,747) $  (2,174) $  (3,921)
                                                    -------  -------  -------  -------  --------  ---------  ---------
                                                    -------  -------  -------  -------  --------  ---------  ---------
Pro forma net loss per share......................                    $ (0.52) $ (0.55) $  (0.61) $   (0.12) $   (0.22)
                                                                      -------  -------  --------  ---------  ---------
                                                                      -------  -------  --------  ---------  ---------
Pro forma weighted average shares outstanding.....                     10,715   17,653    17,664     17,663     17,664
</TABLE>
 
   
<TABLE>
<CAPTION>
                                                                      MARCH 31, 1996
                                                                 ------------------------
                                                                                  AS
                                                                  ACTUAL      ADJUSTED (2)
                                                                 --------     -----------
<S>                                                              <C>          <C>
BALANCE SHEET DATA:
Cash, cash equivalents, and short-term investments............... $ 34,837    $100,997
Total assets.....................................................   41,185     107,345
Long-term obligation.............................................      898         898
Deficit accumulated during development stage.....................  (36,437)    (36,437)
Total shareholders' equity.......................................   34,652     100,812
</TABLE>
    
 
- -------------
(1) Excludes  2,191,518  shares  of  Common  Stock  issuable  upon  exercise  of
    outstanding  options  under the  Company's  1993 Stock  Plan.  Also excludes
    203,881 shares  issuable upon  the exercise  of warrants  outstanding as  of
    March  31, 1996.  See "Management  -- Stock  Plans" and  Note 6  of Notes to
    Financial Statements.
 
   
(2) As adjusted to  reflect the  sale of the  6,000,000 shares  of Common  Stock
    offered by the Company hereby at an assumed initial public offering price of
    $12.00  per share and  the receipt of the  estimated net proceeds therefrom.
    See "Use of Proceeds."
    
 
    UNLESS OTHERWISE INDICATED, ALL INFORMATION CONTAINED IN THIS PROSPECTUS (I)
ASSUMES NO EXERCISE OF THE UNDERWRITERS' OVER-ALLOTMENT OPTION; (II) REFLECTS  A
2-FOR-3  REVERSE STOCK  SPLIT PRIOR  TO THE  EFFECTIVENESS OF  THIS REGISTRATION
STATEMENT; AND (III) GIVES EFFECT TO THE CONVERSION OF ALL OUTSTANDING SHARES OF
PREFERRED STOCK INTO COMMON STOCK UPON THE CLOSING OF THIS OFFERING.
 
                                       5
<PAGE>
                                  RISK FACTORS
 
    In  addition to the other information in this Prospectus, the following risk
factors should  be  considered  carefully  in evaluating  the  Company  and  its
business  before  purchasing shares  of the  Common  Stock offered  hereby. This
Prospectus  contains  forward-looking   statements  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 in  the following risk factors  and elsewhere in this
Prospectus.
 
EARLY STAGE OF DEVELOPMENT
 
    The Company  is  at an  early  stage of  development.  The Company  has  not
commercialized  significant quantities of products based on its technologies. As
of March 31, 1996,  the Company had  placed only nine  GeneChip systems, all  of
which  have  been solely  for  research use  and only  five  of which  have been
purchased by customers. Substantially  all of the  Company's revenues have  been
derived from payments from collaborative research and development agreements and
government research grants.
 
    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  in the  future. The
Company may need to undertake costly  and time-consuming efforts to obtain  this
approval.  There  can be  no assurance  that any  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 a direct sales force  and entering into collaborative  arrangements
to  market its  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.  See  "Management's  Discussion  and  Analysis  of
Financial Condition and Results of Operations."
 
UNCERTAINTIES RELATING TO TECHNOLOGICAL APPROACHES; NEED FOR ADDITIONAL RESEARCH
AND DEVELOPMENT
 
    The Company  intends  to  develop  its  GeneChip  system  for  genomics  and
diagnostics applications. The GeneChip system involves several new technologies,
including  a complex  chemical synthesis process  necessary to  create DNA probe
arrays. In addition, 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
not been previously used in commercial  applications. As the system is 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
reduce the size of its  probe arrays, increase the  number of features on  these
arrays,  develop  instruments capable  of processing  the information  from such
probe arrays, and design  software capable of  managing such information.  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
successful  commercialization. The Company's GeneChip  technology will also need
to  compete  against  well-established  techniques  and  enhancements  to   such
techniques  for analyzing genes  and for diagnostics. There  can be no assurance
that the GeneChip system will  replace or compete successfully against  existing
techniques  and instruments.  Furthermore, there  can be  no assurance  that the
Company's GeneChip technology  will be  useful in providing  information on  the
function of genes or for the analysis of larger sequences of genes.
 
    The  development  of  diagnostic  and  therapeutic  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
 
                                       6
<PAGE>
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 result
in any commercially viable products. See "Business -- Technology."
 
UNCERTAINTY OF MARKET ACCEPTANCE
 
    The commercial success  of the  Company's GeneChip system  will depend  upon
market acceptance by academic research centers, pharmaceutical and biotechnology
companies  and  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 on  the Company's  probe arrays. Market
acceptance may be adversely affected by ethical concerns that may limit the  use
of  the GeneChip system  for certain diagnostic 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.
 
    Potential customers  of  the  GeneChip  system  will  need  to  acquire  the
Company's  fluidics station and probe array scanner  in order to utilize the DNA
probe arrays.  The cost  of  this instrumentation  may deter  certain  potential
customers  from purchasing probe arrays. The Company may be required to discount
the price of its GeneChip  system in order to  place the system with  customers.
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 academic  research
centers,  pharmaceutical  or biotechnology  companies or  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 academic research centers, pharmaceutical and biotechnology  companies
and 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  successfully   market  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
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.
See "Business -- Business Strategy" and "-- Sales and Marketing."
 
UNCERTAINTIES RELATED TO THE HIV PROBE ARRAY
 
    The first commercial application of the Company's GeneChip system is an  HIV
probe array 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. The  Company has placed  only five HIV  probe arrays at
customer sites to date,  all in the  United States. These  systems have been  in
operation  for only a  limited period of  time, and their  accuracy and efficacy
have not been fully demonstrated. There are other uncertainties relating to  the
system,  including that  the Company  has no  prior experience  in introducing a
commercial product, that technicians may encounter difficulties with the  system
that would prevent
 
                                       7
<PAGE>
or limit its use, and that the Company will rely on third parties to manufacture
and  service its  instruments. Furthermore, there  can be no  assurance that the
accuracy of the HIV probe array in providing sequence information from HIV  will
be better than current technologies, such as gel-based sequencing techniques.
 
    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 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.  In  addition,  cost  containment
pressures  for treating HIV patients may limit the price the Company may be able
to charge potential customers for its HIV probe array. There can be no assurance
that  the  HIV  probe  array  will  provide  useful  diagnostic  and  monitoring
information,  that it will  operate without difficulties,  that technicians will
have adequate  training  to  use  the  system, or  that  the  Company  will  not
experience  manufacturing or marketing difficulties  selling the HIV probe array
to academic  research centers,  pharmaceutical and  biotechnology companies  and
reference  laboratories. Furthermore,  there can  be no  assurance that  the HIV
probe array  will  gain regulatory  approval  for clinical  use.  The  Company's
product  revenues in the  near term are dependent  upon the commercialization of
the HIV probe  array. There  can be  no assurance  that these  revenues will  be
realized  in the near  term, or at  all. Failure of  the Company to successfully
commercialize the HIV probe  array 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 any future products  it
may develop. See "Business -- Business Strategy" and "-- Sales and Marketing."
 
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,  at March  31,  1996, the  Company had  an accumulated
deficit of  approximately  $36.4 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 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. See "Management's Discussion and
Analysis of Financial Condition and Results of Operations."
 
PROFITABILITY UNCERTAIN
 
    The Company has experienced substantial operating losses and has never  been
profitable.  The Company expects that  it 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,  product mix  and the  degree of  price discounts  required  to
market   its  products   to  academic   research  centers,   pharmaceutical  and
biotechnology  companies  and  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  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 successfully commercialize any product or that the Company will
achieve product  revenues or  profitability.  See "Management's  Discussion  and
Analysis of Financial Condition and Results of Operations."
 
FLUCTUATIONS IN OPERATING RESULTS
 
    The  Company's quarterly operating  results will depend  upon the volume and
timing of orders for  GeneChip systems and probe  arrays received and  delivered
during  the  quarter,  variations in  payments  under  collaborative agreements,
including milestones, royalties, license fees, and other contract revenues,  and
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
 
                                       8
<PAGE>
competitors; regulatory actions;  market acceptance of  the GeneChip system  and
other   potential   products;  adoption   of  new   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. See "Management's Discussion  and Analysis of Financial
Condition and Results of Operations."
 
INTENSE COMPETITION; RAPID TECHNOLOGICAL CHANGE
 
    Competition in genomics and diagnostics is intense and expected to increase.
Further, the  technologies for  discovering  genes 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,  Boehringer  Mannheim  GmbH,  Hoffmann-LaRoche,  Inc.   ("Roche"),
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
amounts of genetic information. In the genomics field, competitive  technologies
include gel-based sequencing using instruments provided by companies such as the
Applied  Biosystems division of Perkin Elmer  and Pharmacia Biotech AB. 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.
 
    The market for diagnostic 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 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.
 
    In  the genomics  field, future competition  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, Human  Genome
Sciences,    Inc.,   Incyte   Pharmaceuticals,   Inc.   ("Incyte"),   Millennium
Pharmaceuticals, Inc., Myriad Genetics, Inc. and Sequana Therapeutics, Inc. have
significant needs for genomic information and  may choose to develop or  acquire
competing technologies to meet these needs.
 
    Genomics  and  diagnostic 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 is no  assurance that the  Company will be  able to make  the
enhancements  to  its technology  necessary to  compete successfully  with newly
emerging technologies.  See  "Business  -- Research  and  Development"  and  "--
Competition."
 
                                       9
<PAGE>
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 HP and GI.
 
    In November 1994, the Company entered into a collaborative agreement with HP
to develop an advanced scanner  for use with the  GeneChip probe arrays. The  HP
scanner  is currently under development and, in 1997 the Company expects that HP
will be the sole source of its scanners. Accordingly, if the HP scanner does not
become available on a  timely basis or  fails to meet  its performance and  cost
specifications,  it  would  have  a material  adverse  effect  on  the Company's
business.
 
    The Company has  two agreements with  GI, dated November  1994 and  December
1995, relating to use of GeneChip technology to measure gene expression in order
for GI to develop new therapeutic proteins. If GI is not successful in using the
GeneChip  technology  or  if  the  Company  fails  to  maintain  a  satisfactory
relationship with  GI,  the Company  could  lose significant  revenues  and  its
ability  to  obtain  additional  collaborations with  other  companies  would be
impaired.
 
    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. 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  parallel   development  by   a  partner   of  alternative
technologies or components  of 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  consultants and  collaborators are  complex.
There  may  be provisions  within such  agreements which  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. See "Business -- Collaborative Agreements and
Grants."
 
NEED FOR ADDITIONAL FUNDING; UNCERTAINTY OF ACCESS TO CAPITAL
 
    The  Company anticipates that its  existing capital resources, together with
the net proceeds of this offering and interest earned thereon, will enable it to
maintain currently  planned  operations through  at  least 1998.  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
additional capital  will  be  substantial  and  will  depend  on  many  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 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
 
                                       10
<PAGE>
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 through 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."
 
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  tests, 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 gene-based diagnostic  tests marketed by other companies  could
encounter specific difficulties, resulting in societal and governmental concerns
regarding genetic testing.
 
    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 positive  genetic predisposition due  to the increased  risk for  disease
resulting  in possible cost increases for health insurance and the potential for
lost employment time.  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  materially adversely affect  market acceptance of  the
Company's GeneChip system. See "Business -- Government Regulation."
 
LIMITED MANUFACTURING CAPABILITY; SOLE SOURCE SUPPLIERS
 
    The  Company has  limited experience  manufacturing products  for commercial
purposes. To date,  the Company  has a  small scale  facility providing  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  automated manufacturing  capabilities. The  Company may  also need to
comply with the current good  manufacturing practices ("GMP") 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 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 each  probe array. It  is therefore possible
that defective probe arrays might not be identified before they are shipped. 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.
 
                                       11
<PAGE>
    As the  Company's  technologies  evolve, new  manufacturing  techniques  and
systems  will be required. For example,  it is anticipated that batch 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.  The  Company
will  rely  on a  single manufacturing  facility  for its  probe arrays  for the
foreseeable future. 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.
 
    Certain  key parts of the GeneChip system,  such as the probe array scanner,
the fluidics station, and certain reagents, are currently available only from  a
single  source or a few  sources. The Company currently  obtains the scanner for
its GeneChip probe arrays from Molecular Dynamics, Inc. ("Molecular  Dynamics").
The  Company is dependent on Molecular  Dynamics for quality testing and service
of this instrument. The Company has entered into an agreement with HP to  supply
a new scanner for the GeneChip system, which the Company expects to be available
for  commercialization in 1997.  The Company's ability  to commercialize a probe
array with more  features is  dependent upon  successful development  of the  HP
scanner. The Company has contracted with RELA, Inc. ("RELA"), a private company,
to supply the fluidics station that is part of the GeneChip system. The fluidics
stations of the nine GeneChip systems placed to date are prototypes manufactured
by  the Company and not  supplied by RELA. No assurance  can be given that probe
array scanners, fluidics stations  or reagents 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 suppliers 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.
 
    The  GeneChip system is a complex set  of instruments and includes DNA probe
arrays, which  are  produced  in an  innovative  and  complicated  manufacturing
process. During the beta testing phase of the GeneChip system's development, the
Company  and its  vendors have encountered  and addressed a  number of technical
problems, including software failures, improper alignment of probe array wafers,
valve and  tube failures  in  the fluidics  station,  sensor wiring  issues  and
scanner control problems. Due to the complexity and lack of 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, which  would have  a
material  adverse  effect on  the  Company's business,  financial  condition and
results of operations. See "Business -- Manufacturing."
 
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 March 31, 1996, the Company had placed
nine GeneChip systems, of  which only five  had been sold.  The Company has  not
placed  any  of its  GeneChip  systems outside  the  United States.  The Company
intends to market its products to academic research centers, pharmaceutical  and
biotechnology  companies  and  reference laboratories.  The  Company  intends to
market diagnostic tests through a direct sales force to its potential  customers
for  research use only.  The Company intends  to market the  GeneChip system for
genomic   applications   through   collaborations   with   pharmaceutical    and
biotechnology  companies. The Company  anticipates a long  sales cycle to market
the GeneChip system to its potential customers. The Company will be required  to
enter  into  collaboration  or distribution  arrangements  to  commercialize its
products 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. See "Business -- Sales and Marketing."
 
UNCERTAINTIES RELATED TO 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
 
                                       12
<PAGE>
grants  from  government  agencies such  as  the National  Institutes  of Health
("NIH"). Research  funding  by the  government,  however, may  be  significantly
reduced  under several  budget proposals  being discussed  by the  United States
Congress. 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. Proposed legislation being
debated in the  United States  Congress would  eliminate or  reduce the  program
under which the Company's Advanced Technology Program ("ATP") grant is funded by
the  Department of  Commerce. There  can be no  assurance that  the Company will
receive the entire  $20.8 million  of funding designated  for it  under the  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 grants from the Departments of Commerce and Energy and the NIH
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. See "Business -- Collaborative Agreements and Grants."
 
UNCERTAINTIES RELATED TO THIRD-PARTY REIMBURSEMENT
 
    The  Company's ability to successfully commercialize its products may depend
on the Company's ability to obtain adequate levels of third-party  reimbursement
for  use of  certain diagnostic  tests in  the United  States, Europe  and other
countries. Currently, availability of  third-party reimbursement is limited  and
uncertain for genetic tests.
 
    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 device or diagnostic test  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 Company's  ability
to  commercialize certain of its products  successfully may depend on the extent
to which appropriate  reimbursement levels for  the costs of  such products  and
related  treatment  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
medical  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 services
and products, as well as legislative  proposals to reform health care or  reduce
government insurance programs, may all result in lower prices for certain of the
Company's products. The cost containment measures that health care providers are
instituting  and the  results of  any health care  reform could  have an adverse
effect on the Company's ability to sell  certain of its products and may have  a
material  adverse  effect on  the  Company's business,  financial  condition and
results of operations.
 
GOVERNMENT REGULATION; NO ASSURANCE OF REGULATORY APPROVAL
 
    The  Company  anticipates  the  manufacturing,  labeling,  distribution  and
marketing of some or all of the Company's diagnostic products will be subject to
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 analytes,  and 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 recently proposed a rule that, if
adopted, would regulate the  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 testing 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  will  be
regulated as medical devices.
 
                                       13
<PAGE>
    Medical  devices  generally  require  FDA  approval  or  clearance  prior to
marketing in  the United  States. The  process of  obtaining FDA  clearances  or
approvals  necessary to market medical  devices can be time-consuming, expensive
and uncertain, and  there can  be no assurance  that any  clearance or  approval
sought  by  the Company  will be  granted or  that FDA  review will  not involve
delays, adversely affecting the  marketing and sale  of the Company's  products.
Further,  clearance  or  approval  may  place  substantial  restrictions  on the
indications for which the product may be marketed or to whom it may be marketed.
Additionally, there can  be no assurance  that FDA will  not request  additional
data or request that the Company conduct further clinical studies.
 
    If  approval  or  clearance is  obtained,  the  Company will  be  subject to
continuing FDA obligations. When manufacturing medical devices, the Company will
be required to adhere  to regulations setting forth  current GMP, which  require
that  the  Company  manufacture  its  products and  maintain  its  records  in a
prescribed manner with  respect to  manufacturing, testing  and quality  control
activities.  In addition, among other requirements, the Company will be required
to comply  with FDA  requirements  for labeling  and  promotion of  its  medical
devices.  Further, if the Company wanted to  make changes on a product after FDA
clearance or approval, including changes in indications or intended use or other
significant  modifications  to  labeling,   manufacturing  or  product   design,
additional clearances or approvals would be required from the FDA.
 
    Failure  to obtain required  regulatory approval or  clearance or failure to
obtain timely approval or clearance, or the imposition of stringent labeling  or
sales  restrictions on  the Company's  products, could  have a  material adverse
effect on the Company. In addition, failure to comply with applicable regulatory
requirements could subject the Company to enforcement action, including  product
seizures,  recalls, withdrawal  of clearances  or approvals,  restrictions on or
injunctions against marketing  the Company's  products, and  civil and  criminal
penalties,  any one or more of which could have a material adverse effect on the
Company.
 
    Medical device laws  and regulations are  also in effect  in many  countries
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. Failure to comply with applicable state and foreign
medical device laws and  regulations may have a  material adverse effect on  the
Company's business, financial condition and results of operations.
 
    The  Company is also  subject to numerous environmental  and safety laws and
regulations, including  those  governing  the  use  and  disposal  of  hazardous
materials.  Any violation of, and the cost of compliance with, these regulations
could adversely affect  the Company's  operations. See  "Business --  Government
Regulation."
 
DEPENDENCE ON PROPRIETARY TECHNOLOGY AND UNPREDICTABILITY OF PATENT PROTECTION
 
    As  of April  15, 1996, Affymetrix  had exclusive licenses  from Affymax for
over 20 patents  and patent  applications in the  United States  related to  its
business in the fields of clinical diagnostics and research supply. In addition,
Affymetrix  is  the assignee  of 52  United States  patent applications  and one
issued patent in the United States. Many of these patents and applications  have
been  filed  and/or issued  in one  or more  foreign countries.  Affymetrix also
relies upon  those  patents,  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 copyright and trade secrets  and to operate without infringing  the
proprietary rights of third parties.
 
    The  Company  is  party  to  various  license  option  agreements (including
agreements with Affymax, Stanford University  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  technology
under  commercially reasonable terms could have an adverse effect on the ability
of the Company to sell certain of its products.
 
    The patent positions of pharmaceutical, biopharmaceutical 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
 
                                       14
<PAGE>
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 if
it is required to defend itself in  patent suits brought by third parties or  if
it initiates such suits.
 
    Others  may  have  filed  and  in  the  future  are  likely  to  file patent
applications that are similar or identical to those of the Company. 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 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, and there is
no assurance such a license will be available on commercially reasonable  terms.
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  these patents, other patents or proprietary
rights of third parties. In  addition, the Company has  received and may in  the
future  receive  notices claiming  infringement from  third  parties as  well as
invitations to take licenses under third party patents. Any 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  partner  to obtain  a  license in  order  to
continue to manufacture or market the affected products and processes. There can
be  no assurance that the Company or its collaborative partners would prevail in
any such  action or  that  any license  (including  licenses proposed  by  third
parties)  required under any such patent 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. If the Company  becomes
involved  in  such litigation,  it could  consume a  substantial portion  of the
Company's managerial  and  financial  resources, which  could  have  a  material
adverse  effect on  the Company's business,  financial condition  and results of
operations.
 
    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  meaningfully
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
 
                                       15
<PAGE>
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.  See  "Business --
Intellectual Property."
 
ATTRACTION AND RETENTION OF KEY EMPLOYEES AND CONSULTANTS
 
    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  objectives. 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. See "Business -- Scientific Advisory Board."
 
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 clinical
liability insurance. 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.
 
BROAD DISCRETION IN ALLOCATION AND USE OF PROCEEDS
 
   
    Although the Company  expects to  use approximately $55,000,000  of the  net
proceeds  of  this  offering  for research  and  development,  including product
development and core research, manufacturing  scale-up, and to expand sales  and
marketing  capabilities, the Company has not yet identified the specific amounts
and uses of approximately $11,000,000  (approximately 17%) 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 offering. See "Use of Proceeds."
    
 
CONTROL BY GLAXO, MANAGEMENT AND RELATED PERSONS
 
   
    Upon completion of  this offering,  Glaxo will  indirectly beneficially  own
34.3%  of  the  Company's  outstanding  Common  Stock  and  executive  officers,
directors  and  principal  shareholders  (other  than  Glaxo)  will   indirectly
beneficially  own 14.3% 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. See "Principal Shareholders" and "Certain Transactions."
    
 
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
 
                                       16
<PAGE>
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.
 
NO PRIOR TRADING MARKET FOR COMMON STOCK; POSSIBLE VOLATILITY OF STOCK PRICE;
DILUTION
 
    Prior  to this offering, there  has been no public  market for the Company's
Common Stock, and there can  be no assurance that  an active public market  will
develop  or be sustained after this  offering. The initial public offering price
will be determined by negotiations among the Company and the Representatives  of
the  Underwriters  and  may  not  be indicative  of  future  market  prices. See
"Underwriting" for a discussion of the  factors to be considered in  determining
the  initial public  offering price. The  trading price of  the Company's Common
Stock could be subject to significant fluctuations in response to  announcements
of  results  of  research  activities,  collaborative  agreements, technological
innovations, or new commercial products  by the Company, collaborative  partners
or  competitors, changes in government  regulations, regulatory actions, changes
in patent laws, developments concerning proprietary rights, quarterly variations
in operating results,  litigation and other  events. 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.
 
    Purchasers  of  the Common  Stock will  incur  an immediate  and substantial
dilution in the net  tangible book value  of the Common  Stock from the  initial
public  offering price. Additional dilution is  likely to occur upon exercise of
options granted by the Company. See "Dilution."
 
SHARES ELIGIBLE FOR FUTURE SALE; POSSIBLE ADVERSE EFFECT ON FUTURE MARKET PRICE
 
   
    Future sales of  substantial amounts of  the Company's Common  Stock in  the
public market after this offering could adversely affect the market price of the
Common Stock. Of the 22,239,231 shares to be outstanding after the offering, the
6,000,000  shares of  Common Stock offered  hereby (plus any  shares issued upon
exercise of the  Underwriters' over-allotment option)  will be freely  tradeable
without  restriction.  Beginning 90  days  after June    , 1996  (the "Effective
Date"), approximately 50,100 additional shares will be eligible for sale in  the
public  market subject  to compliance with  Rule 701. In  addition, beginning 90
days after the  Effective Date  approximately 186,140 shares  subject to  vested
options  will be available for sale subject to compliance with Rule 701. Certain
shareholders of the  Company, including the  officers, directors, employees  and
the  affiliates of the  Company are subject  to contractual "lock-up" agreements
generally providing that they  will not offer, sell,  contract to sell or  grant
any option to purchase or otherwise dispose of the shares of Common Stock of the
Company  or any  securities exercisable  for or  convertible into  the Company's
Common Stock owned by  them for a  period of 180 days  after the Effective  Date
without  the prior written consent of Robertson  Stephens & Company. As a result
of these contractual restrictions, notwithstanding possible earlier  eligibility
for  sale under the provisions of Rules 144, 144(k) and 701 under the Securities
Act of  1933, as  amended  (the "Securities  Act"),  shares subject  to  lock-up
agreements  will not be saleable  until such agreements expire  or are waived by
Robertson Stephens  & Company.  Beginning  180 days  after the  Effective  Date,
approximately 10,411,408 additional shares will become eligible for sale subject
to  the provisions of  Rule 144 or Rule  701 upon the  expiration of the lock-up
agreements not to sell such shares. Beginning 180 days after the Effective Date,
approximately 183,366  additional  shares  subject to  vested  options  will  be
available  for sale subject to  compliance with Rule 701  upon the expiration of
lock-up agreements not to sell such  shares. Robertson, Stephens & Company  may,
in  its  sole discretion  and at  any time  without notice,  release all  or any
portion of  the  securities subject  to  lock-up agreements.  In  addition,  the
Company intends to register on Form S-8 under the Securities Act within 180 days
after  the Effective Date shares of Common Stock issued or reserved for issuance
under the Company's 1993 Stock Plan (the "Stock Plan"), and the 1996 Nonemployee
Directors Stock Option Plan (the  "Directors Plan") and such registrations  will
be effective on filing. As of March 31, 1996, there were outstanding options for
the  purchase of  2,191,518 shares  under the Stock  Plan, of  which options for
158,490 shares were exercisable.  No shares have been  issued to date under  the
Directors  Plan. As of  April 30, 1996, the  holders of approximately 15,834,537
shares are entitled to certain registration rights with respect to such  shares.
If a large
    
 
                                       17
<PAGE>
number  of such shares were registered and sold in the public market, such sales
could have an adverse effect on the market price for the Company's Common Stock.
If the Company were required to include in a Company-initiated registration  the
shares  held  by such  holders pursuant  to the  exercise of  their registration
rights, such sales may have an adverse effect on the Company's ability to  raise
needed  capital. See "Management -- Stock  Plans," "Description of Capital Stock
- -- Registration Rights  of Certain  Shareholders," "Shares  Eligible for  Future
Sale," and "Underwriting."
 
                                       18
<PAGE>
                                USE OF PROCEEDS
 
   
    The  net proceeds to  the Company from  the sale of  the 6,000,000 shares of
Common Stock offered by the Company hereby at an assumed initial public offering
price of  $12.00  per  share  are  estimated  to  be  approximately  $66,160,000
($76,204,000  assuming the  Underwriters' over-allotment option  is exercised in
full), after deducting the underwriting discounts and commissions and  estimated
offering expenses payable by the Company.
    
 
   
    The  Company intends to use  the net proceeds from  this offering to develop
new products and  applications for  the GeneChip  system. Such  products may  be
developed  by the Company internally or through collaborative arrangements using
the Company's  existing technology  and products  or complementary  products  or
technologies   acquired  from  third  parties.  While  such  collaborations  and
acquisitions may represent a significant use of the proceeds of the offering, no
significant acquisitions  are  currently planned.  The  Company expects  to  use
approximately  $30  million  for  research  and  development,  including product
development  and   core  research;   approximately  $18   million  for   capital
expenditures,  including  scale-up of  manufacturing, facilities  and laboratory
equipment; and approximately $7  million for expansion  of sales and  marketing.
The  Company will  use the balance  of approximately  $11 million (approximately
17%) of  the  net proceeds  for  working  capital and  other  general  corporate
purposes.  The Company's  Board of  Directors and  management will  retain broad
discretion as to the allocation of the net proceeds of the offering.
    
 
    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
development of  manufacturing, marketing  and sales  capabilities. Pending  such
uses,  the  Company intends  to  invest the  net  proceeds of  this  offering in
short-term, investment-grade, interest-bearing securities.
 
                                DIVIDEND POLICY
 
    The Company has never paid dividends since its inception and does not intend
to pay any dividends in the foreseeable future. The Company currently intends to
retain any future earnings to fund the development of its business.
 
                                       19
<PAGE>
                                 CAPITALIZATION
 
   
    The following table sets forth the capitalization of the Company as of March
31, 1996, (i) on a pro forma basis to give effect to the automatic conversion of
all outstanding shares of the Company's  Preferred Stock into Common Stock  upon
the  closing of this offering and (ii) as adjusted to reflect the receipt of the
estimated net proceeds  from the sale  of the 6,000,000  shares of Common  Stock
offered hereby, at an assumed initial public offering price of $12.00 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>
                                                                                                MARCH 31, 1996
                                                                                           ------------------------
                                                                                            PRO FORMA   AS ADJUSTED
                                                                                           -----------  -----------
                                                                                                (in thousands)
<S>                                                                                        <C>          <C>
Noncurrent portion of capital lease obligation (1).......................................   $     898    $     898
Shareholders' equity:
  Preferred stock; no par value, 27,500,000 shares authorized; pro forma and as adjusted,
   no shares issued and outstanding......................................................      --           --
  Common stock; no par value, 50,000,000 shares authorized;
   pro forma 16,239,231 issued and outstanding; as adjusted,
   22,239,231 issued and outstanding (2).................................................      73,528      139,688
  Notes receivable from officers.........................................................         (41)         (41)
  Unrealized gain on available-for-sale securities.......................................           1            1
  Deferred compensation..................................................................      (2,399)      (2,399)
  Deficit accumulated during the development stage.......................................     (36,437)     (36,437)
                                                                                           -----------  -----------
    Total shareholders' equity...........................................................      34,652      100,812
                                                                                           -----------  -----------
      Total capitalization...............................................................   $  35,550    $ 101,710
                                                                                           -----------  -----------
                                                                                           -----------  -----------
</TABLE>
    
 
- ------------
(1) See Note  5  of Notes  to  Financial Statements  for  a description  of  the
    Company's obligation under 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) 2,191,518
    shares issuable upon exercise of outstanding options at March 31, 1996, at a
    weighted average price of $0.65 per share and (iii) 965,228 shares of Common
    Stock reserved  for future  issuance  under the  Stock Plan.  Also  excludes
    300,000  shares reserved  for issuance under  the Directors  Plan, which was
    adopted in April 1996. See "Management --  Stock Plans" and Note 6 of  Notes
    to Financial Statements.
 
                                       20
<PAGE>
                                    DILUTION
 
   
    The  pro forma net tangible  book value of the Company  as of March 31, 1996
was $34,652,000 or approximately  $2.13 per share. Pro  forma 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 March 31, 1996.  Pro forma net tangible  book value dilution per
share represents the difference between the amount per share paid by  purchasers
of  shares of  Common Stock in  the offering made  hereby and the  pro forma net
tangible book value  per share  immediately after completion  of this  offering.
After giving effect to the estimated net proceeds from the sale of the 6,000,000
shares  of Common  Stock offered  hereby at  an assumed  initial public offering
price of  $12.00  per share,  after  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 March  31, 1996 would  have
been  $100,812,000  or  approximately  $4.53 per  share  of  Common  Stock. This
represents an immediate increase in net  tangible book value of $2.40 per  share
to  existing shareholders  and an immediate  dilution in pro  forma net tangible
book value of $7.47 per  share to purchasers of  Common Stock in this  offering.
The following table illustrates this per share dilution:
    
 
   
<TABLE>
<S>                                                                    <C>        <C>
Assumed public offering price........................................             $   12.00
  Pro forma net tangible book value as of March 31, 1996.............  $    2.13
  Increase attributable to new investors.............................       2.40
                                                                       ---------
Pro forma net tangible book value after the offering.................                  4.53
                                                                                  ---------
Dilution to new investors............................................             $    7.47
                                                                                  ---------
                                                                                  ---------
</TABLE>
    
 
    The  following table summarizes, on a pro  forma basis as of March 31, 1996,
the number of shares of Common Stock purchased from the Company, the total  cash
consideration  paid  and  the  average  price per  share  paid  by  the existing
shareholders and by  new investors before  deducting the underwriting  discounts
and  commissions and estimated  offering expenses payable by  the Company at the
assumed initial public offering price of $12.00 per share:
 
   
<TABLE>
<CAPTION>
                                           SHARES PURCHASED         TOTAL CONSIDERATION
                                        -----------------------  -------------------------  AVERAGE PRICE
                                           NUMBER      PERCENT       AMOUNT       PERCENT     PER SHARE
                                        ------------  ---------  --------------  ---------  -------------
<S>                                     <C>           <C>        <C>             <C>        <C>
Existing shareholders.................    16,239,231       73.0% $   70,860,000       49.6%   $    4.36
New investors.........................     6,000,000       27.0      72,000,000       50.4        12.00
                                        ------------  ---------  --------------  ---------
  Total...............................    22,239,231      100.0% $  142,860,000      100.0%
                                        ------------  ---------  --------------  ---------
                                        ------------  ---------  --------------  ---------
</TABLE>
    
 
    The foregoing  table assumes  no exercise  of outstanding  stock options  or
warrants.  As of  March 31,  1996, there  were outstanding  warrants to purchase
203,881 shares of  Common Stock  at an  exercise price  of $8.25  per share  and
outstanding options to purchase an aggregate of 2,191,518 shares of Common Stock
at  a weighted average exercise price of $0.65 per share. To the extent that any
of these options or  warrants or additional options  or warrants are  exercised,
there will be further dilution to new investors. See "Management -- Stock Plans"
and Note 6 of Notes to Financial Statements.
 
                                       21
<PAGE>
                            SELECTED FINANCIAL DATA
 
    The  statement  of  operations data  set  forth  below for  the  years ended
December 31, 1993, 1994 and 1995 and  the balance sheet data as of December  31,
1994  and 1995 are derived  from financial statements of  the Company audited by
Ernst & Young LLP,  independent auditors, which are  included elsewhere in  this
Prospectus.  The statement of  operations data for the  years ended December 31,
1991 and 1992 and the balance sheet data as of December 31, 1991, 1992, and 1993
are derived from financial  statements audited by Ernst  & Young LLP, which  are
not  included in this Prospectus.  The balance sheet data  at March 31, 1996 and
the statement of operations data for the  three months ended March 31, 1995  and
1996  and for the period from inception (January  1, 1991) to March 31, 1996 are
derived  from  unaudited  financial   statements  included  elsewhere  in   this
prospectus.   The  unaudited  financial   statements  include  all  adjustments,
consisting only  of normal  recurring adjustments,  that the  Company  considers
necessary  for  a fair  presentation of  the financial  position and  results of
operations for these periods. Operating results for the three months ended March
31, 1996 are not necessarily indicative of the results that may be expected  for
the entire year ending December 31, 1996. The Company has never declared or paid
any  cash dividends  on shares of  its capital  stock. The data  set forth below
should be  read in  conjunction with  "Management's Discussion  and Analysis  of
Financial  Condition and  Results of  Operations" and  the Financial Statements,
related Notes thereto,  and other  financial information  included elsewhere  in
this Prospectus.
 
<TABLE>
<CAPTION>
                                                                                                                PERIOD FROM
                                                                                         THREE MONTHS ENDED      INCEPTION
                                                                                                                (JANUARY 1,
                                                YEAR ENDED DECEMBER 31,                      MARCH 31,         1991) THROUGH
                                 -----------------------------------------------------  --------------------     MARCH 31,
                                   1991       1992       1993       1994       1995       1995       1996          1996
                                 ---------  ---------  ---------  ---------  ---------  ---------  ---------  ---------------
                                                            (in thousands, except per share data)
<S>                              <C>        <C>        <C>        <C>        <C>        <C>        <C>        <C>
STATEMENT OF OPERATIONS DATA:
Contract and grant revenue.....  $  --      $      43  $   1,413  $   1,574  $   4,625  $     854  $   1,416     $   9,071
Operating expenses:
  Research and development.....      1,576      4,106      6,566      9,483     12,420      2,274      4,177        38,328
  General and administrative...        261        582        577      2,303      3,833        777      1,649         9,205
                                 ---------  ---------  ---------  ---------  ---------  ---------  ---------       -------
    Total operating expenses...      1,837      4,688      7,143     11,786     16,253      3,051      5,826        47,533
                                 ---------  ---------  ---------  ---------  ---------  ---------  ---------       -------
Loss from operations...........     (1,837)    (4,645)    (5,730)   (10,212)   (11,628)    (2,197)    (4,410)      (38,462)
  Interest income..............     --              3        211        575      1,301        183        517         2,607
  Interest expense.............     --            (18)       (73)       (43)      (420)      (160)       (28)         (582)
                                 ---------  ---------  ---------  ---------  ---------  ---------  ---------       -------
Net loss.......................  $  (1,837) $  (4,660) $  (5,592) $  (9,680) $ (10,747) $  (2,174) $  (3,921)    $ (36,437)
                                 ---------  ---------  ---------  ---------  ---------  ---------  ---------       -------
                                 ---------  ---------  ---------  ---------  ---------  ---------  ---------       -------
Pro forma net loss per share
 (1)...........................                        $   (0.52) $   (0.55) $   (0.61) $   (0.12) $   (0.22)
                                                       ---------  ---------  ---------  ---------  ---------
                                                       ---------  ---------  ---------  ---------  ---------
Pro forma weighted average
 shares outstanding (1)........                           10,715     17,653     17,664     17,663     17,664
</TABLE>
 
<TABLE>
<CAPTION>
                                                                    DECEMBER 31,
                                                -----------------------------------------------------   MARCH 31,
                                                  1991       1992       1993       1994       1995        1996
                                                ---------  ---------  ---------  ---------  ---------  -----------
                                                                   (in thousands)
<S>                                             <C>        <C>        <C>        <C>        <C>        <C>
BALANCE SHEET DATA:
Cash, cash equivalents and short-term
 investments..................................  $  --      $      94  $  20,392  $  17,805  $  38,883   $  34,837
Working capital...............................          1       (320)    17,452     15,677     36,070      31,729
Total assets..................................          1        813     22,817     19,861     44,552      41,185
Long-term obligations.........................     --            564     --          7,135        948         898
Deficit accumulated during development
 stage........................................     (1,837)    (6,497)   (12,089)   (21,769)   (32,516)    (36,437)
Total shareholders' equity (net capital
 deficiency)..................................          1       (181)    19,214      9,170     38,519      34,652
</TABLE>
 
- ---------------
(1)  See  Note 1  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.
 
                                       22
<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  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 "Risk Factors" and elsewhere in
this Prospectus.
 
OVERVIEW
 
    Affymetrix  is  a development  stage  company which  is  developing GeneChip
systems and related applications and technologies for the acquisition,  analysis
and  management of complex  genetic information. The  business and operations of
Affymetrix were commenced in 1991 by 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. In September 1993, Affymetrix
issued equity  securities  through  a private  financing  of  approximately  $21
million  that reduced  Affymax' ownership to  approximately 65%.  In March 1995,
Glaxo acquired  Affymax,  including  its then  majority  ownership  interest  in
Affymetrix. In August 1995, Affymetrix issued equity securities through a second
private  financing  of  approximately  $39  million,  further  reducing Affymax'
percentage ownership.  Glaxo  currently  indirectly owns  approximately  46%  of
Affymetrix.
 
    The  Company  has a  limited operating  history that,  to date,  has focused
primarily on the development of its technology. Based on its GeneChip technology
platform, Affymetrix is developing a portfolio of products for academic research
centers, pharmaceutical and biotechnology companies and reference  laboratories.
As  of March 31, 1996, the Company had  placed nine of its GeneChip systems with
customers for  validation, initial  testing and  certain research  applications.
Only  five of the systems have been  purchased by customers, three of which were
for the HIV application.  The payments received from  the sale of these  systems
were  recorded  as contract  revenues  pursuant to  development  agreements. The
Company commercially introduced its first  product, the GeneChip system and  the
HIV  probe array for research use only, in April 1996. Failure of the Company to
successfully develop, manufacture and market  additional products over the  next
several  years  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  net  losses  of approximately  $10.7  million during  the  year ended
December 31, 1995, and at March 31, 1996, the Company had an accumulated deficit
of approximately $36.4 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 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  and  marketing
capabilities.
 
    The  Company's quarterly operating  results will depend  upon the volume and
timing of orders for  GeneChip systems and probe  arrays received and  delivered
during  the  quarter,  variations in  payments  under  collaborative agreements,
including milestones, royalties, license fees, and other contract revenues,  and
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  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.
 
    The  Company expects that it 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,  product mix and  the degree of  price discounts required  to market its
products to academic research centers,
 
                                       23
<PAGE>
pharmaceutical companies  and  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  collaborative arrangements and on the  ability
of  the  Company and  its collaborative  partners to  successfully commercialize
products incorporating  the  Company's  technologies.  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.
 
    From  inception  through March  31, 1996,  the  Company has  generated $11.7
million from government  grants, collaborative agreements  and interest  income.
The  Company has  significant collaborative relationships  with GI and  HP and a
significant grant  from the  National Institute  of Standards  and  Technology's
Advanced  Technology Program.  The Company  began its  collaboration with  GI in
November  1994  to  develop   applications  of  the   GeneChip  system  to   the
identification  of new genes and new  uses of genes using expression monitoring.
Under this  agreement,  GI  funded  the  Company's  research  to  determine  the
feasibility  of  this  application of  GeneChip  technology and  agreed  to make
milestone and royalty payments.  In December 1995, GI  and the Company signed  a
second  agreement for  the supply  of custom  probe arrays  to GI  in return for
up-front fees, milestone payments and royalties for products developed from  use
of  the probe  arrays. As  of March  31, 1996,  the Company  recognized contract
revenues totaling  $1.3  million  from GI.  As  a  result of  entering  into  an
agreement with Incyte in April 1996, Affymetrix is required to refund 30% of the
development  funding  received  from  GI  and future  funding  from  GI  will be
proportionally reduced.  The  Company recorded  an  accrued liability  for  this
refund and believes that the reduction of future funding from GI will not have a
material effect on its operations. See "Business -- Collaborative Agreements and
Grants."
 
    The  Company  entered  into a  collaboration  with  HP in  November  1994 to
develop, manufacture  and  supply a  more  advanced  scanner for  use  with  the
Company's  GeneChip probe arrays and for  the Company, in collaboration with HP,
to develop,  manufacture and  supply certain  probe  arrays to  HP for  sale  in
certain  markets. As of March 31, 1996, the Company recognized contract revenues
totaling $1.5 million from HP.
 
    In October 1994,  the Company  and Molecular Dynamics  received a  five-year
grant  from  the  National  Institute  of  Standards  and  Technology's Advanced
Technology Program in the amount of $31.5 million to develop a miniaturized  DNA
diagnostic  system based  on the  Company's technology.  Pursuant to  the grant,
$20.8 million is  designated for the  Company and its  subcontractors and  $10.7
million  is designated for Molecular Dynamics and its subcontractors, subject to
the requirements of each company  to match such funding.  As of March 31,  1996,
the Company's revenues from this grant totaled $1.6 million.
 
    Collaborations  will continue  to be an  important element  of the Company's
business strategy. There can be  no assurance that the  Company will be able  to
maintain  existing collaborations,  enter into future  collaborations to develop
applications of its GeneChip system or that any such collaborative  arrangements
will be successful.
 
RESULTS OF OPERATIONS
 
  THREE MONTHS ENDED MARCH 31, 1996 AND MARCH 31, 1995
 
    Contract and grant revenue increased by 66% for the three months ended March
31,  1996 to  $1.4 million from  $854,000 for  the three months  ended March 31,
1995. The  increase was  principally due  to  the sale  of one  GeneChip  system
pursuant to a development agreement in the first quarter of 1996, as compared to
none in the first quarter of 1995, and an increase in ATP grant revenue.
 
   
    Research  and development expenses  increased to $4.2  million for the three
months ended March 31, 1996 compared to $2.3 million for the three months  ended
March  31,  1995.  The increase  was  attributable  primarily to  the  hiring of
additional research and development personnel, costs incurred to further product
development in anticipation of Affymetrix' initial product launch, and  purchase
of  research  supplies.  Affymetrix anticipates  that  research  and development
expenses will continue to increase in future periods.
    
 
   
    General and administrative expenses increased to $1.6 million for the  three
months  ended March  31, 1996  compared to $777,000  for the  three months ended
March 31,  1995.  The  increase  in  general  and  administrative  expenses  was
primarily  due to the hiring of additional management personnel and to legal and
other professional
    
 
                                       24
<PAGE>
   
fees in  connection  with  the  overall  scale-up  of  operations  and  business
development  efforts.  General  and  administrative  expenses  are  expected  to
increase significantly in future periods  to support Affymetrix' operations  and
business development efforts.
    
 
   
    Interest  income  was $517,000  for the  three months  ended March  31, 1996
compared to $183,000 for the three months ended March 31, 1995. The increase was
primarily attributable to the  investment of the net  proceeds from the  private
placement  of Series  B Senior  Convertible Preferred  Stock in  August 1995 and
higher interest rates.  Interest expense for  the three months  ended March  31,
1996 decreased by $132,000 as compared to the three months ended March 31, 1995,
primarily  due  to the  conversion of  a  $6.0 million  subordinated convertible
promissory note held by Affymax in August 1995.
    
 
  YEARS ENDED DECEMBER 31, 1995 AND DECEMBER 31, 1994
 
    Contract and grant  revenue increased  to $4.6  million for  1995 from  $1.6
million  for 1994 as a result primarily of its ATP grant and revenue earned from
collaborative agreements with GI and HP.
 
    Research and  development  expenses  increased to  $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 increased  to  $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 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.
 
  YEARS ENDED DECEMBER 31, 1994 AND DECEMBER 31, 1993
 
    Contract  and grant  revenue increased  to $1.6  million for  1994 from $1.4
million for 1993 as a result of additional funding from government grants.
 
    Research and  development  expenses  increased  to  $9.5  million  for  1994
compared  to $6.6  million for  1993. The  increase in  research and development
expenses was attributable  primarily to  the hiring of  additional research  and
development personnel and increased purchases of research supplies.
 
    General  and  administrative expenses  increased  to $2.3  million  for 1994
compared to  $577,000  for 1993.  The  increase in  general  and  administrative
expenses  was attributable primarily to  the hiring of additional administrative
personnel and the incurring of legal  and other professional fees in  connection
with the expansion of Affymetrix' operations.
 
    Interest  income was  $575,000 for 1994  compared to $211,000  for 1993. The
increase resulted from the investment of net proceeds from the private placement
of Series A Senior Convertible Preferred Stock in September 1993.
 
LIQUIDITY AND CAPITAL RESOURCES
 
    Since inception, Affymetrix  has financed its  operations primarily  through
private  placements of equity securities, contributions from Affymax, government
grants, collaborative agreements, issuances of convertible debt, equipment lease
financings and interest income. Through March 31, 1996, Affymetrix has  received
net  cash of $71.4 million from  financing activities, consisting principally of
approximately $53.6 million from issuances of common and preferred stock,  $10.6
million  from  contribution by  Affymax, $7.1  million  from issuances  of notes
payable, and $1.3 million in lease financing. As of March 31, 1996, $1.1 million
of notes have  been repaid, $6.0  million of convertible  notes held by  Affymax
have  been converted into shares of Series B Senior Convertible Preferred Stock,
and $10.6 million of contributions from Affymax have been converted to shares of
Series 1 Subordinated Convertible Preferred Stock.
 
                                       25
<PAGE>
    Affymetrix' net cash used in operating  activities was $3.1 million for  the
three months ended March 31, 1996, $10.2 million for 1995, $7.4 million for 1994
and  $3.2 million for 1993.  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.  Affymetrix  has also
received collaborative  research and  government  grant funding  totaling  $11.0
million,  of  which  $9.1 million  has  been  recognized as  contract  and grant
revenue.
 
   
    The cash used  by the Company  in investing activities  since its  inception
through  March  31, 1996  totaled  $41.0 million.  Capital  expenditures totaled
$701,000 for the three months ended March 31, 1996. Capital expenditures totaled
$2.3 million in 1995, $1.2 million in  1994 and $1.5 million in 1993.  Purchases
of  available-for-sale securities were  $2.0 million for  the three months ended
March 31, 1996  and $38.4  million, $3.0 million,  and $14.0  million for  1995,
1994,   and  1993,   respectively.  Proceeds   from  sales   and  maturities  of
available-for-sale securities were $3.6 million for the three months ended March
31, 1996 and  $14.0 million and  $5.3 million for  1995 and 1994,  respectively.
There were no sales or maturities in 1993.
    
 
    As  of March 31, 1996, Affymetrix had cash, cash equivalents, and short-term
investments of  $34.8  million.  The Company  anticipates  that  these  existing
capital  resources, together with the net proceeds of this offering and interest
earned thereon, will enable it to maintain currently planned operations  through
at  least  1998. However,  this expectation  is based  on the  Company's current
operating plan,  which could  change 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  continues to  have sufficient  funds for  its operating  plan. The Company's
requirements for additional capital will be substantial and will depend on  many
factors,  including payments received under  existing and possible 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, sales and
marketing capabilities. The Company  has no credit  facility or other  committed
sources  of capital.  To the extent  capital resources,  including payments from
existing and possible future collaborative agreements and grants, together  with
the  net  proceeds  of the  offering  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  through entering into
collaborative agreements on unattractive terms. The Company's inability to raise
capital would  have  a  material  adverse  effect  on  the  Company's  business,
financial condition and results of operations.
 
    Affymetrix  expects  its  capital  requirements to  increase  over  the next
several years as it expands its facilities and acquires scientific equipment  to
support  manufacturing  and  research  and  development  efforts.  The Company's
expenditure requirements will depend on numerous factors, including the progress
of its research and  development programs; the  development of commercial  scale
manufacturing  capabilities;  its  ability  to  maintain  existing collaborative
arrangements and  establish and  maintain  new collaborative  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.
 
    At  December  31, 1995,  Affymetrix'  net operating  loss  carryforwards and
research tax credit  carryforwards for  income tax  purposes were  approximately
$22.0 million and $1.2 million, respectively. 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. If not utilized,the carryforwards expire at various dates beginning
in  2008 through 2010. As a result of  the annual limitation, a portion of these
carryforwards may expire before ultimately  becoming available to reduce  income
tax liabilities.
 
                                       26
<PAGE>
                                    BUSINESS
 
    The  following  Business section  contains forward-looking  statements 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 "Risk Factors"  and
elsewhere in this Prospectus.
 
OVERVIEW
 
    Affymetrix 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 system consists of disposable DNA probe arrays containing
gene  sequences on a chip, instruments to process the probe arrays, and software
to analyze  and manage  genetic information.  The Company  commenced  commercial
sales  of the GeneChip  system and a HIV  probe array for  research use in April
1996.
 
BACKGROUND
 
  GENES AND DISEASE
 
    Genes provide  the  fundamental basis  for  understanding human  health  and
disease.  Genomics, the  study of  genes and their  functions, will  lead to new
approaches to diagnose, monitor and treat 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 other strand. Only certain pairs of nucleotide bases
can form these bonds:  A always pairs with  T, and C always  pairs with G.  Such
paired  DNA  strands are  said to  be  complementary. When  two DNA  strands are
complementary, they bind  together to form  a double helix  in a process  called
hybridization.  In humans, the DNA molecule  contains 3 billion nucleotide pairs
organized into 46  chromosomes. The  human genome  is believed  to contain  over
100,000 genes.
 
    Cells  carry  out  their  normal biological  functions  through  the genetic
instructions encoded  in their  DNA.  This 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.  Each   organism's  characteristics   are  thus  ultimately
determined by proteins encoded in its DNA. This process is illustrated below.
 
                                   [DIAGRAM]
 
                                       27
<PAGE>
    The diversity of living organisms results from variability in their genomes.
Variability  stems  from  differences  in  the  sequences  of  genes  and   from
differences  in gene expression. 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  organism. However, in  other cases, polymorphisms  can result in
altered function 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  cardiovascular  disease. Similarly,  it has
recently been discovered that polymorphisms in the genome of HIV, the virus that
causes AIDS,  enable  that  virus  to develop  resistance  to  antiviral  drugs,
resulting  in disease progression  and ultimately death.  In order to understand
how mutations in particular genes  cause disease, scientists must compare  genes
from  healthy  and  diseased  people.  These  efforts  are  laborious  and  time
consuming, requiring the  repeated sequencing of  genes from a  large number  of
people.
 
    The  genes expressed, as  well as the  order and level  of their expression,
determine differences  among cell  types  in an  organism. Although  most  cells
contain  an organism's full set  of genes, only a small  fraction of this set is
expressed in each cell. The expression of  the wrong or defective genes, or  the
expression  of  too  much or  too  little  of genes  normally  expressed, causes
disease. Such abnormalities in gene  expression have been associated with  human
diseases, including many types of cancer. The role of gene expression in disease
requires  an  understanding  of how  genes  interact  to cause  disease  and how
external stimuli, such as drugs, cause variations in gene expression.
 
  THE ROLE OF GENOMICS IN UNDERSTANDING DISEASE
 
    Increased knowledge  of how  DNA molecules  encode the  functions of  living
organisms  has generated  a worldwide effort  to identify and  sequence genes of
many organisms, including the estimated  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 of each gene  and
its  role in disease. This research, commonly  referred to as genomics, may lead
to new opportunities in drug discovery and diagnostics.
 
    The general processes by which researchers are attempting to discover  genes
fall   into  two  principal  categories:  genetic  mapping  and  high-throughput
sequencing.  Once  a  gene  has  been  identified,  either  through  mapping  or
high-throughput sequencing, researchers must understand the function of the gene
and  how variability in the  gene leads to disease.  Many diseases are caused by
either changes in the sequence  of the gene or by  changes in the expression  of
the  gene.  Understanding  the  role  of  a  gene  in  disease  requires  either
quantitative gene expression monitoring or large scale polymorphism screening.
 
                                       28
<PAGE>
                                    [CHART]
 
             THE  CHART  ABOVE   ILLUSTRATES  TECHNIQUES  USED   TO
             IDENTIFY  GENES AND UNDERSTAND  THEIR FUNCTIONS, WHICH
             CAN LEAD  TO THE  DEVELOPMENT  OF NEW  DIAGNOSTIC  AND
             THERAPEUTIC OPPORTUNITIES.
 
    GENETIC  MAPPING.  Researchers  use genetic mapping to  identify the gene or
genes causing an observable and well-characterized disease or genetic  disorder.
The  gene mapping process is extensive and typically begins by assembling tissue
samples and histories from families where the disease of interest is  prevalent.
Researchers  then attempt to locate the position of the gene responsible for the
disease using a technique called linkage analysis. This technique relies on  the
identification  of  genes using  DNA  sequences called  markers,  whose specific
locations are known among the three billion  base pairs of the human genome.  By
comparing the patterns of markers in generations of healthy and diseased people,
researchers  can link genes  to markers and thereby  determine that a particular
marker is  located near  the gene  responsible for  the disease.  By using  more
markers,  genes can be more precisely mapped. Since many major diseases, such as
diabetes and atherosclerosis,  are believed  to be  caused by  the interplay  of
numerous   genes,  it   is  often  necessary   to  try  to   map  several  genes
simultaneously. This mapping process requires extensive efforts and  significant
computational  capabilities.  It  is  expected  that  increasing  the  speed and
accuracy of genetic  mapping and  improving the ability  to analyze  information
from thousands of different markers may accelerate the identification of disease
genes.
 
    HIGH-THROUGHPUT  SEQUENCING.    High-throughput  sequencing  involves  first
identifying genes and subsequently determining their function and possible  role
in  disease. When a  gene is expressed in  a particular cell,  its DNA is copied
into messenger RNA. In this process, sequences that do not code for an expressed
gene are removed. Thus,  messenger RNA contains  only expressed gene  sequences.
Using high-throughput sequencing methods, DNA copies of the messenger RNA can be
sequenced  and thereby  reveal the sequence  of a gene.  Corporate, academic and
government efforts have been successful  in identifying a substantial number  of
the 100,000 genes in the human genome using such techniques.
 
    GENE  EXPRESSION MONITORING.  By monitoring the expression of a large number
of genes, researchers seek  to correlate changes in  expression patterns with  a
particular disease. The effectiveness of monitoring gene
 
                                       29
<PAGE>
expression  is  a  function  of  the  number  of  genes  that  can  be monitored
simultaneously,  the  sensitivity  (ability  to  measure  low  levels  of   gene
expression)   and  the  ability  of  the  method  used  to  provide  qualitative
information.  Relative  levels  of  gene  expression  are  currently   monitored
primarily  through  an intensive  process of  sequencing  many copies  of genes.
Scientists believe that the development of technologies that can  quantitatively
monitor  thousands of  genes simultaneously  will increase  the effectiveness of
gene expression monitoring  as a tool  for understanding the  roles of genes  in
disease.
 
    POLYMORPHISM  SCREENING.  Using polymorphism  screening, 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 statistically correlate specific gene mutations
with the disease. Currently,  the polymorphism screening  process is done  using
gel-based  sequencing. A  typical polymorphism  screening project  might require
sequencing 10 genes of 5,000 nucleotide bases each in up to 1,000 patients, or a
total of 50  million bases,  to understand  the role of  these 10  genes in  one
disease.  Using high-throughput sequencing  techniques, even at  a cost of cents
per base, such projects  are expensive and time  consuming. It is expected  that
new  technologies will  be needed  to effectively  screen the  more than 100,000
human genes for polymorphisms that correlate with many known diseases.
 
  OPPORTUNITIES IN DIAGNOSTICS AND THERAPEUTICS
 
    Current diagnostic tests can monitor  the physiological effects of  disease,
detect infectious organisms by growing them in culture, or use specific markers,
such  as proteins, known to be associated with disease. Diagnostic tests rely on
a patient  sample of  tissue,  blood, or  urine,  and detect  the  physiological
effect,  the  infectious organism  or the  marker, in  the sample.  For example,
immunoassays detect and measure specific proteins already known to be associated
with a  disease  using antibodies  generated  against those  proteins.  However,
protein  markers  are  not  available  or are  not  useful  for  diagnosing many
diseases. Diagnostic tests that monitor  physiological effects are also  limited
because  different diseases can cause the  same effect. For example, an elevated
white blood cell  count can  be caused by  appendicitis, an  acute infection  or
leukemia.
 
    Most  infectious  diseases  are  viral, bacterial  or  fungal.  Diagnosis of
bacterial and  fungal infections  is generally  achieved by  growing a  culture,
which  may take several days. Even  after the infectious organism is identified,
further analysis may be required to determine which antibiotics, if any, may  be
effective  in  treating the  disease.  In the  case  of many  viruses, diagnosis
depends on immunoassay tests that detect antibodies to the virus. However, these
tests provide  no information  as to  whether  the virus  is resistant  to  drug
therapy or if the infection is active or latent.
 
    Recent  advances  in  gene-based  diagnostic  tests  using  DNA  probes, DNA
amplification techniques and sequencing technologies have begun to address these
shortcomings by directly  examining the  genes associated with  a given  disease
rather  than  relying on  physiological parameters  or antibodies.  For example,
amplification of specific genes from an infectious organism eliminates the  need
to grow that organism in culture.
 
    However,  current techniques for gathering genetic information for diagnosis
and monitoring of  disease have limitations.  For example, gel-based  sequencing
techniques   used  in  some  approaches   are  time-consuming,  require  skilled
operators, and can analyze only limited lengths of contiguous DNA sequences in a
given run. Gene-based diagnosis often requires rapid turnaround and  examination
of  noncontiguous DNA sequences. As a result, new techniques and tools are being
developed to improve the diagnosis, monitoring and treatment of disease.
 
                                       30
<PAGE>
    Using  genetic mapping and high-throughput  sequencing, scientists have been
successful in discovering many  genes. Technological improvements that  increase
the  speed and decrease the cost  of gene expression monitoring and polymorphism
screening will improve the ability of researchers to understand the function  of
these  genes  and  their role  in  disease.  Such knowledge  may  assist  in the
development of therapeutics  with greater  efficacy and fewer  side effects,  as
well as diagnostic products with greater sensitivity and accuracy.
 
BUSINESS STRATEGY
 
    Affymetrix' objective is to establish the 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, instruments to process the probe arrays, and  software
to  analyze and  manage genetic information  from the probe  arrays. The Company
intends to commercialize the  GeneChip system in  two principal areas:  genomics
and diagnostics.
 
  GENOMICS
 
    - ESTABLISH  GENECHIP TECHNOLOGY  AS A  PLATFORM FOR  GENOMICS RESEARCH. The
      Company intends  to  develop  the  GeneChip  system  for  use  in  several
      applications  where Affymetrix believes it has substantial advantages over
      conventional tools used for DNA sequence analysis in the identification of
      genes and their role  in disease. Initially,  four such applications  have
      been  identified: gene discovery, gene mapping, gene expression monitoring
      and polymorphism screening, all of which require analyzing and  processing
      large amounts of genetic information.
 
    - COMMERCIALIZE  CUSTOM  PROBE  ARRAYS THROUGH  CORPORATE  PARTNERSHIPS. The
      Company  intends  to  sell  custom  probe  arrays  to  pharmaceutical  and
      biotechnology companies through collaborative agreements. The Company will
      seek  to receive revenues  through design and  development fees, milestone
      payments  and  sales  of   DNA  probe  arrays   and  instruments  to   the
      collaborative  partner.  If  the collaborative  partner  is  successful in
      discovering products  through  the use  of  the GeneChip  technology,  the
      Company  would  also  seek to  receive  royalties  from the  sale  of such
      products.
 
    - PARTICIPATE IN  THE COLLECTION  AND  APPLICATION OF  GENETIC  INFORMATION.
      Affymetrix  intends to use  the DNA sequence  analysis capabilities of the
      GeneChip  technology  to  measure  gene  expression  in  order  to  create
      databases  containing information on the function  of genes and their role
      in disease. Affymetrix anticipates that  such databases will be  developed
      and   commercialized   through   partnerships   with   pharmaceutical  and
      biotechnology companies.
 
  DIAGNOSTICS
 
    - IMPROVE ACCURACY AND SPEED OF DIAGNOSIS. Affymetrix intends to develop DNA
      probe arrays to obtain  genetic information from  patient samples so  that
      specific diseases can be rapidly diagnosed. Furthermore, such probe arrays
      will   be   designed   to  simultaneously   collect   additional  relevant
      information, including drug resistance data.
 
    - ESTABLISH DIRECT  SALES EFFORTS  AND PARTNERSHIPS.  Affymetrix intends  to
      initially market its GeneChip products, for research use only, directly to
      academic  research  centers and  reference  laboratories that  conduct the
      majority of gene-based  diagnostic tests.  In addition,  the Company  will
      seek  to partner  with, or  license technology  to, established diagnostic
      companies which could develop, seek regulatory approval, and commercialize
      probe arrays for broader clinical use.
 
    - DISCOVER NOVEL DIAGNOSTIC MARKERS. The Company intends to use  information
      from  the  Human  Genome Project  and  related efforts  to  identify genes
      associated with particular diseases and use the proteins encoded by  these
      genes  in  new diagnostic  tests. The  Company will  seek to  partner with
      established diagnostic companies by providing these novel protein  markers
      for development and commercialization as conventional immunoassays.
 
    There   can  be  no  assurance  that  the  Company  will  be  successful  in
implementing its strategy or  marketing its GeneChip  system for these  genomics
and    diagnostic    applications.   The    Company's   GeneChip    system   and
 
                                       31
<PAGE>
   
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 approvals, the Company expects that such approvals
will be required for diagnostic applications in the future. The Company may need
to undertake costly  and time-consuming  efforts to  obtain required  approvals.
There  can be no assurance that any  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.
    
 
TECHNOLOGY
 
   
    Affymetrix' probe  array  technology  and  systems  integrate  semiconductor
fabrication  techniques, molecular biology, solid  phase chemistry, software and
robotics. The  Company's  GeneChip system  consists  of four  integrated  parts:
disposable DNA probe arrays containing genetic information on a chip housed in a
cartridge,  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,  analyze  and  manage  the  genetic  information. The
GeneChip  system  is  designed  for  use  by  pharmaceutical  and  biotechnology
companies,  academic research centers  and reference laboratories.  The price of
the  Company's  GeneChip  system,  excluding  probe  arrays,  is   approximately
$120,000.  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.
    
 
    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.  This  process uses  technology  initially
developed  at  Affymax  and exclusively  licensed  to the  Company  for selected
applications. 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.
 
          ILLUSTRATION OF THE LIGHT DIRECTED PROBE ARRAY SYNTHESIS PROCESS
 
                               [DIAGRAM]
 
    The Company  uses  photolithography  to  synthesize  large  numbers  of  DNA
sequences simultaneously in specific locations on a glass chip. Photolithography
is  a  technique  which uses  light  to  induce chemical  reactions  that create
exposure patterns on the glass chip. The process begins by coating the chip with
light-sensitive chemical compounds (defined as "protecting" groups) that prevent
chemical coupling. 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
 
                                       32
<PAGE>
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 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 single probe arrays.
 
    Each probe array  contains thousands  of "features."  Each feature  contains
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.
 
                               [DIAGRAM]
 
    The Company's GeneChip  technology enables  it to  effectively synthesize  a
large  number  of  DNA sequences,  which  would  not be  possible  with existing
technologies. Unlike  conventional  synthesis,  which generally  uses  a  linear
process   to   create   compounds,  the   Company's   synthesis   technology  is
combinatorial, in that the number  of compounds synthesized grows  exponentially
with  the number of cycles in the synthesis. For example, in a 40 cycle process,
Affymetrix has  produced a  probe array  with over  one million  features,  each
containing  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 test sample is then washed over the probe array surface
and the labeled test sample binds, or hybridizes, 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
and  sequence of the  nucleic acid sample  can be determined  by detecting these
signals since the sequence and position  of each complementary DNA probe on  the
probe array are known. The Company's currently manufactured probe arrays contain
from 16,000 to more than 100,000 features.
 
                                       33
<PAGE>
    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 excited by
the light from the laser. The intensity of the fluorescent signal is recorded by
the scanner and stored in the  computer. The current scanner can read  1.28X1.28
centimeter probe arrays with up to 64,000 features. An advanced scanner is being
developed to read 1.28X1.28 centimeter probe arrays with up to 400,000 features.
However,  there  can be  no  assurance that  this  scanner will  be successfully
developed or commercialized.
 
    SOFTWARE.   The  GeneChip  product  software is  supplied  as  part  of  the
integrated  system and  runs on a  Windows 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  HIV  GeneChip
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  compare
genetic sequences across test samples.
 
GENOMICS APPLICATION AREAS
 
    Affymetrix  is applying  the GeneChip  technology to  create a  platform for
genomics  and  pharmaceutical  research.  Genomics  applications  include   gene
discovery, genetic mapping, expression monitoring and polymorphism screening.
 
    GENE  DISCOVERY.   The  discovery  of genes  may  be an  important  means to
understand disease and  to design  new therapies. A  large number  of the  genes
identified  to date have been classified into families based on common sequences
within these genes. One approach to  gene discovery uses these common  sequences
to search for and identify previously unknown members of these gene families. To
facilitate  this approach,  the Company  designs DNA  probe arrays  containing a
large number of  probes for  both common and  variable regions  of known  genes.
Using  this technology,  samples containing DNA  are screened  against the probe
arrays, and, for  genes that  are already known,  both the  variable and  common
regions  are detected  from the sample.  For previously unknown  genes, only the
common regions are detected, thus identifying a new gene.
 
    The Company believes that this approach to gene discovery may accelerate the
rate of  new gene  identification. In  November 1994,  Affymetrix established  a
collaboration  with GI to apply the GeneChip  technology to the discovery of new
genes and uses of genes in selected  gene areas. As part of this  collaboration,
GI  and the  Company have  undertaken a  three-year research  project whereby GI
provides research funding. In addition, Affymetrix supplies custom probe  arrays
to GI for specified fees and may receive milestone payments and royalties.
 
    GENETIC  MAPPING.    Genetic  mapping is  an  important  method  for linking
diseases to particular genes. Over the last five years, over 60 genes have  been
linked  to known diseases by this  method. However, the current technologies for
mapping genes are  slow and labor  intensive. This problem  is exacerbated  when
looking at complex diseases such as diabetes, asthma, and cardiovascular disease
which  are believed to be associated with multiple genes. Using genetic mapping,
researchers attempt  to find  disease genes  by using  markers. The  correlation
between  markers in diseased and healthy people enables researchers to link such
genes to a particular disease state.  Research to identify markers is  currently
being  conducted by  various academic and  scientific groups  to improve genetic
mapping techniques.  The  Company  has  established  a  collaboration  with  the
Whitehead  Institute for Biomedical  Research at the  Massachusetts Institute of
Technology ("MIT")  to  design  probe  arrays with  new  markers  identified  by
Whitehead    scientists.    The    Company    intends    to    develop   mapping
 
                                       34
<PAGE>
probe arrays  based upon  publicly available  markers as  well as  custom  probe
arrays  based  upon proprietary  markers. The  Company  intends to  market these
arrays to  pharmaceutical and  biotechnology  companies for  conducting  genetic
mapping.  There  can be  no  assurance that  these  arrays will  be successfully
developed or marketed to these or other customers.
 
    EXPRESSION  MONITORING.    Currently,  large  amounts  of  genetic  sequence
information  are being generated,  through the Human  Genome Project and related
efforts, yet relatively little is understood  about the function of most  genes.
Affymetrix   believes  that  monitoring  gene   expression  is  fundamental  for
understanding the function of genes and their role in disease. To facilitate the
monitoring of gene expression, the Company designs probe arrays with DNA  probes
that  are complementary to  a sequence within  a gene of  interest. By providing
sequence information, these probe arrays may enable researchers to identify  the
particular  gene and quantitatively measure its  level of expression compared to
other genes of interest in the test sample. By synthesizing specific probes  for
multiple  genes on a single probe array, the Company also 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  gene
expression  and how it  is related to disease  progression. The Company believes
that such  information will  be an  important  tool in  the development  of  new
therapeutics.
 
    Under its collaboration with GI established in November 1994, the Company is
receiving   research  funding  to  develop  probe  arrays  for  gene  expression
monitoring. The Company will also  design, manufacture, and supply custom  probe
arrays for GI pursuant to a second agreement executed in December 1995. Multiple
custom  DNA  probe  arrays  will  be designed  by  the  Company  to  monitor the
expression patterns of  approximately 15,000  genes to  be specified  by GI.  GI
retains  all rights to  discovered genes and their  uses. Affymetrix will supply
custom probe arrays for  specified fees and may  receive milestone payments  and
royalties  on certain  therapeutic products  based on  the discovered  genes. In
April 1996, the Company  also entered into an  agreement with Incyte to  explore
the potential use of DNA probe arrays in the area of gene expression.
 
    POLYMORPHISM  SCREENING.  As  the identity of  genes in the  human genome is
determined, the  need  to understand  the  significance of  the  variability  of
nucleotide  sequences in these  genes increases. Researchers  must determine the
normal sequence  of the  gene, which  mutations exist  and how  these  mutations
correlate  with a disease. This requires the  sequencing of samples from a large
number of  affected  and  unaffected individuals.  Using  sequencing  strategies
developed  for  the HIV  probe array,  Affymetrix  believes that  GeneChip probe
arrays could significantly reduce the  cost and time of polymorphism  screening,
which  is  currently  done  through more  labor  intensive  gel-based sequencing
techniques. In May  1996, the Company  entered into an  agreement with Glaxo  to
design,  test  and supply  probe  arrays to  demonstrate  use of  the  arrays in
detecting polymorphisms in specific genes. Glaxo and Affymetrix will design  and
test  a probe array containing several genes specified by Glaxo. If successfully
developed, Affymetrix will supply Glaxo's requirements of such probe arrays  for
research purposes.
 
    There  can be  no assurance that  the Company's  collaborative partners will
perform their obligations as expected or will devote sufficient resources to the
development, testing or marketing of the Company's potential products  developed
under  the collaborations. Further, there can  be no assurance that any products
for genomics  applications  will be  successfully  developed, be  proven  to  be
accurate  and  efficacious  in any  markets,  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.
 
DIAGNOSTIC PRODUCTS AND RESEARCH APPLICATIONS
 
    Affymetrix  intends to use the GeneChip  platform in conjunction with public
and private  gene databases  to discover  and develop  diagnostic products.  The
Company  is pursuing diagnostic products and research applications in infectious
diseases, cancer and other areas, including drug metabolism.
 
    INFECTIOUS DISEASES.    The Company  believes  its GeneChip  technology  may
enable  it  to  develop tests  which,  by  sequencing large  amounts  of genetic
information and quantitatively measuring levels of gene expression, can  provide
information that could improve treatments for many infectious diseases.
 
                                       35
<PAGE>
    Industry sources estimate that in North America and Europe approximately 1.5
million persons are infected with HIV and that approximately 100,000 persons are
diagnosed  with AIDS annually.  Many HIV symptomatic  patients receive antiviral
treatment with  reverse  transcriptase  inhibitors, such  as  AZT,  or  protease
inhibitors,  both of which  block proteins required for  the virus to replicate.
The HIV  genome encodes  the reverse  transcriptase and  protease gene  proteins
within  approximately 1,400  bases (or approximately  15%) of  the viral genome.
Mutations in the viral genome result  from errors in replication. Some of  these
mutations  confer resistance  to the antiviral  drugs being  administered to the
patient. It  is  believed  that  the identity  of  nucleotides  in  the  reverse
transcriptase  and  protease  genes will  be  essential  in order  to  monitor a
patient's drug resistance profile.
 
    Affymetrix has developed the GeneChip system with an HIV probe array as  its
first  product for commercialization. The  Company believes this GeneChip system
will  enable  researchers  to  identify  the  mutations  associated  with   drug
resistance  in  HIV  infected patients  and  allow researchers  to  identify new
mutations. The  HIV probe  array  contains DNA  probes in  approximately  20,000
features  that  represent sequences  of the  reverse transcriptase  and protease
genes of the virus. These features can identify mutations at any of the sites in
the genes that have been associated with drug resistance. The Company expects to
initially market the HIV product for research use in identifying the correlation
between mutations in the  virus and drug resistance.  The Company believes  that
monitoring  drug  resistance  related  mutations  during  therapy  may  become a
valuable aspect  of  patient management.  Affymetrix  has placed  five  GeneChip
systems  for  the  HIV  application  in  academic  research  and  pharmaceutical
companies for evaluation and validation. The Company commenced commercial  sales
of  the GeneChip system and HIV probe array for research use only in April 1996.
The  Company  will  rely  on  third  parties  to  manufacture  and  service  its
instruments.  The Company  has no prior  experience in  introducing a commercial
product. There  can  be  no  assurance  that  technicians  will  not  experience
difficulties  with the system that would prevent  or limit its use. In addition,
there can be  no assurance that  the efficiency  and accuracy of  the HIV  probe
array  in providing  sequence information from  HIV will be  better than current
technologies, such as gel-based sequencing.
 
    The Company  intends  to  develop  additional  diagnostic  products  in  the
infectious  disease area that  could determine complex  drug resistance and gene
identification  information.  The  Company  is  evaluating  the  development  of
additional GeneChip probe tests for bacterial, viral and fungal infections, such
as   tuberculosis  and  cytomegalovirus  (CMV).  The  Company  intends  to  seek
collaborators to participate in the funding, development and marketing of  these
tests.
 
    CANCER.  In the United States, approximately 1.1 million new cases of cancer
are  diagnosed  annually and  the incidence  of  cancer deaths  is approximately
520,000 individuals  each year.  Colorectal, breast,  prostate and  lung  cancer
account for approximately half of all diagnoses.
 
    The  p53 gene  encodes a  protein whose normal  function is  to control cell
replication. However, mutations in the p53 gene  can result in the loss of  this
function  and are known to contribute to  the aggressive growth of some types of
cancer, including colorectal,  breast and bladder  cancers. Mutations have  been
observed  to date  at more  than 400  distinct sites  in the  p53 gene sequence.
Currently available diagnostic tests include IN VITRO assays that use antibodies
to detect the accumulation of p53 molecules in cells but cannot directly  detect
mutations  in the p53 gene. Gel-based sequencing methods are impractical because
mutations can occur over a large area  of the genome, requiring many gels to  be
processed  to sequence the entire gene. As a result, these methods are unable to
predict the rate of cancer progression. Understanding the rate of progression is
often necessary  to determine  whether to  treat the  cancer with  chemotherapy,
radiation or surgery.
 
    The Company is currently developing a GeneChip p53 probe array that contains
DNA  probes to detect known mutation sites, as  well as to sequence areas of the
p53 gene where other mutations may occur but have currently not been identified.
Initially, the Company  intends to  market these  p53 probe  arrays to  academic
research  centers and reference laboratories to  study the p53 gene. The Company
also intends to seek regulatory approval to use the p53 probe array for clinical
use to assist in  monitoring cancer progression  and improving patient  therapy.
The  Company  is currently  evaluating other  genes  associated with  cancer for
potential product development.  There can  be no  assurance that  the p53  probe
array  or other cancer products will  be developed, receive regulatory approvals
or be successfully commercialized.
 
                                       36
<PAGE>
    OTHER APPLICATIONS.  The  Company is developing  its GeneChip technology  to
address  other applications in pharmaceutical  research, such as monitoring drug
metabolism.
 
    Monitoring drug metabolism  is an essential  component in drug  development.
Drug  metabolism  determines  how quickly  or  slowly  a drug  is  eliminated or
rendered inactive  and  whether  any of  the  drug  is processed  into  a  toxic
compound.  Genetic differences  among patients are  an important  factor in drug
metabolism. Variations in drug  metabolism are important  to the development  of
new  drugs because these  variations determine how patients  will react to drugs
and which drugs will have relatively uniform effects across a broad  population.
Certain  of  the genes  coding for  metabolic enzymes  have been  identified and
sequenced by researchers. Patients  who have mutations in  these genes are  poor
metabolizers of drugs and may suffer from excessive drug accumulation and severe
toxicity from standard drug doses.
 
    Affymetrix  is collaborating with HP to  develop a GeneChip probe array with
probes containing  the  gene sequence  of  mutations  in two  genes  coding  for
metabolic  enzymes.  Mutations  in these  two  genes have  been  associated with
patients who are  poor metabolizers of  numerous drugs. HP  will have  worldwide
marketing rights for the probe arrays in the nonclinical market, which are to be
manufactured  and supplied by the Company.  The Company is entitled to royalties
and revenues, if any, from the supply of these probe arrays to HP. There can  be
no  assurance that these DNA probe arrays will be developed or commercialized or
will result in revenues to the Company.
 
    NEW DIAGNOSTIC MARKERS.   As genes are discovered  through the Human  Genome
Project  and related efforts, the  Company believes that additional correlations
will be found between genes and disease. Affymetrix believes that by using probe
arrays to monitor the levels of expression of many genes in parallel, it will be
able to identify proteins encoded by these  genes that can serve as new  markers
for   conventional  immunoassays.  The  Company   intends  to  collaborate  with
diagnostic companies  to  incorporate  such  protein  markers  into  established
immunoassay  formats. There can be no assurance that the Company will be able to
identify any new markers, negotiate such collaborative agreements on  acceptable
terms, if at all, or that such collaborations will be successful.
 
    There can be no assurance that any products for diagnostic applications 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.
 
MANUFACTURING
 
    The Company's strategy  is to  manufacture its disposable  DNA probe  arrays
in-house  and contract  with third-party  suppliers to  manufacture the fluidics
station and scanner for its GeneChip system.
 
    The Company is  currently manufacturing limited  quantities of probe  arrays
for  internal  and  collaborative purposes  and  for initial  product  sales for
research use. 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. 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.  The
Company's  probe array  synthesis, dicing  and assembly  processes currently use
robotics and the  Company's manufacturing  process is  partially automated.  The
Company  intends to further automate the  manufacturing process. There can be no
assurance that manufacturing and quality control problems will not arise as  the
Company  attempts to scale-up its manufacturing facilities or that such scale-up
can be  acheived  in  a  timely manner  or  at  commercially  reasonable  costs.
Affymetrix   has   developed   software  programs   that   automatically  design
photolithographic masks used in probe array manufacturing and control the  probe
array manufacturing lines.
 
    The  Company relies on outside vendors  to manufacture its fluidics stations
and scanners. The Company has a supply agreement with Molecular Dynamics for its
current   scanner,    which   can    read   up    to   64,000    features    per
 
                                       37
<PAGE>
1.28X1.28  centimeter probe array.  The Company's HIV  probe array currently has
20,000 features on a 1.28X1.28 centimeter probe  array and may be used with  the
Molecular  Dynamics  scanner.  The  Company expects  to  purchase  scanners from
Molecular Dynamics through the end of 1996.
 
    As part of the  Company's collaboration with HP,  HP is developing a  higher
resolution  scanner. The HP scanner is designed  to read probe arrays with up to
400,000 features per 1.28X1.28 centimeter probe array. The Company expects  that
the  HP scanner will be commercially available  for use with the Company's probe
arrays in 1997.
 
    The fluidics stations  currently in  the field are  prototype versions  that
were manufactured by the Company. The Company has entered into an agreement with
RELA,  a private company, for  the supply of fluidics  stations. Pursuant to the
Company's supply  agreement with  RELA,  the Company  must provide  a  six-month
rolling  forecast  of its  purchase requirements  for  fluidics stations  and is
obligated to make certain  minimum purchases, at prices  that vary depending  on
the volume ordered.
 
    There   can  be  no  assurance  that   the  HP  scanner  will  be  developed
successfully. Further,  no assurance  can be  given that  probe array  scanners,
fluidics  stations or  reagents 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 suppliers  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.
 
    The GeneChip system is a complex  set of instruments and includes DNA  probe
arrays,  which  are  produced  in an  innovative  and  complicated manufacturing
process. During the beta testing phase of the GeneChip system's development, the
Company and its vendors have  encountered and satisfactorily addressed a  number
of  technical problems, including software failures, improper alignment of probe
array wafers, valve  and tube failures  in the fluidics  station, sensor  wiring
issues and scanner control problems. Due to the complexity and lack of 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, which  would
have  a material adverse  effect on the  Company's business, financial condition
and results of operations.
 
    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  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 a commercially reasonable cost.
 
SALES AND MARKETING
 
    The   Company  intends  to   market  the  GeneChip   system  for  diagnostic
applications through direct  sales efforts and  collaborative arrangements  with
corporate  partners and distributors. The Company intends to market the GeneChip
system for genomics applications through collaborations with corporate partners.
The Company's near  term strategy is  to commercialize the  GeneChip system  for
research  use only.  The Company's  longer term  strategy is  to seek regulatory
approval for  and to  commercialize  GeneChip systems  as diagnostic  tests  for
clinical  use. To date, the Company has  placed nine systems for research use in
the United States. Five of these systems are for HIV applications.
 
    The Company believes that the primary market for diagnostic applications  in
the  United  States  will  be  academic  research  centers,  pharmaceutical  and
biotechnology companies  and  reference  laboratories. The  Company  intends  to
establish  a  direct sales  force  to market  to  these potential  customers for
research use. The Company believes that academic research centers could use  the
GeneChip   system  in  their  disease   related  research.  Affymetrix  believes
pharmaceutical  companies  could  use  the  GeneChip  system  to  study  genetic
variations in patients participating in clinical trials of new drugs. Currently,
there  are three major reference laboratory  companies in the United States, two
of   which    are    associated    with    large    pharmaceutical    companies.
 
                                       38
<PAGE>
These  reference laboratories are specialized laboratories at multiple locations
that conduct complex  testing for the  diagnosis and monitoring  of disease  and
clinical  trials and testing for pharmaceutical and biotechnology companies. The
Company believes that each of these  reference laboratories could be a  customer
for  the  GeneChip system  and  may require  multiple  systems at  each location
depending on the volume and complexity of the tests.
 
    The Company believes that the primary international customers for diagnostic
applications  of  its  GeneChip  system  will  be  academic  research   centers,
pharmaceutical    and   biotechnology   companies,   and   independent   testing
laboratories. The Company initially intends to market to these customers through
collaborative partners. To date, the Company has not placed any of its  GeneChip
systems outside the United States.
 
    Affymetrix  believes that the primary customers for genomics applications of
its GeneChip  system will  be pharmaceutical  and biotechnology  companies  that
would  use the GeneChip system in  the discovery of new therapeutics. Affymetrix
intends to  market  to  these  customers  directly  and  to  form  non-exclusive
contracts  for  the  design, manufacture  and  supply of  custom  GeneChip probe
arrays. Affymetrix currently  has a  small internal technical  support group  to
service  its GeneChip system, which the  Company intends to expand as necessary.
The Company believes  that it will  need to develop  a larger technical  support
infrastructure to service these collaborations.
 
    Under the Company's collaboration with HP, HP has worldwide rights to market
GeneChip  systems in specified nonclinical markets.  Affymetrix has the right to
market the system in the clinical  diagnostic market, subject to HP's option  to
certain rights in selected clinical markets.
 
    Market   acceptance  will  depend  on  many  factors,  including  convincing
researchers  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 on the Company's probe arrays. Market acceptance may be  adversely
affected  by ethical concerns that may limit  the use of the GeneChip system for
certain diagnostic  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  centers that are  the potential customers  for the  GeneChip
system. 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  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.
 
RESEARCH AND DEVELOPMENT
 
    The Company believes that substantial investment in research and development
is  essential to obtaining a competitive position in the genetic information and
diagnostics  markets.  Affymetrix  focuses  on  three  types  of  research   and
development:   applied  research,  including  diagnostic  product  research  and
discovery;  core   technology  development,   including  manufacturing   process
refinement,  new instrumentation design, and novel chemical synthesis; and basic
research to explore and  expand the potential  uses of DNA  probe arrays and  to
discover new technologies.
 
    APPLIED  RESEARCH.  Affymetrix  has several diagnostic  research projects in
three major diagnostic fields: infectious disease, cancer and other diseases. In
the infectious disease area, the Company is evaluating probe array  applications
for  several infectious organisms,  such as tuberculosis  and CMV. The Company's
research in cancer  is focused  on monitoring mutations  associated with  cancer
progression  and the discovery of diagnostic  markers for cancers such as breast
and colorectal cancers. The Company has a collaboration with Dr. Francis Collins
at the NIH  for the development  of probe  arrays directed to  the detection  of
certain  mutations  believed to  be associated  with  the development  of breast
cancer.
 
    Other research efforts  at Affymetrix  are currently  focused on  developing
probe  arrays for the diagnosis of genetic diseases and certain other disorders.
Affymetrix  has   conducted   a   feasibility   study   funded   by   Roche   to
 
                                       39
<PAGE>
develop  a probe array  to detect mutations  causing cystic fibrosis. Affymetrix
also intends to initiate research programs based on known markers, such as  HLA,
for  determining compatibility  for tissue  transplants. The  Company intends to
initiate research programs to discover novel markers for prevalent chronic human
diseases, such as cardiovascular disease, osteoporosis and arthritis.
 
    CORE TECHNOLOGY  DEVELOPMENT.   The  Company  conducts research  in  several
areas,   including  novel  and  improved  synthesis  chemistries,  manufacturing
processes, new manufacturing instrumentation, and enhancements in the design  of
fluidics  stations and scanners.  A significant research  effort is dedicated to
designing data analysis software to extract information from DNA probe arrays.
 
    BASIC RESEARCH.  Affymetrix' basic research efforts are focused on expanding
the  applications  of   the  GeneChip   system  and   discovering  related   new
technologies.  These efforts  are focused  on improving  sensitivity, increasing
capacity and conducting more complex assays.
 
    The Company's research and development expenses for the years ended December
31, 1995,  1994 and  1993, were  $12.4 million,  $9.5 million  and $6.6  million
respectively. Research and development expenses for the three-month period ended
March 31, 1996 and 1995 were $4.2 million and $2.3 million, respectively.
 
    Genomics  and  diagnostic technologies  have undergone  and are  expected to
continue  to  undergo   rapid  and  significant   change.  Rapid   technological
development  by the  Company or  others may  result in  products or technologies
becoming obsolete. In  addition, any 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  is no  assurance  that the
Company will be  able to make  the enhancements to  its technology necessary  to
compete successfully with newly emerging technologies.
 
COLLABORATIVE AGREEMENTS AND GRANTS
 
    The  Company's strategy regarding collaborative  agreements is to expand the
applications of the Company's technology and to acquire access to  complementary
technologies  and  resources,  such  as manufacturing  and  marketing,  from its
collaborative  partners.   Accordingly,  the   Company's  agreements   emphasize
preserving  the  Company's  rights  to  technological  improvements  and  future
business opportunities rather than large  up-front fees or sizeable  commitments
of research funding from its partners.
 
  GENETICS INSTITUTE, INC.
 
    In  November  1994, the  Company  entered into  a  collaboration with  GI to
develop and  apply new  technologies for  understanding the  functions of  human
genes.  Under the agreement, GI provides research funding to the Company for the
development of DNA probe arrays  used in DNA sequence  analysis to enable GI  to
discover  new genes and uses for genes  and to rapidly screen for the expression
of specified genes in both normal and diseased tissues.
 
    The initial term of  the research collaboration with  GI is three years.  In
the  event that  the specified technical  milestones are achieved  prior to such
time, GI  and the  Company may  either conclude  the collaboration  or agree  to
continue  the collaboration with additional milestones  for the remainder of the
three years. The  agreement provides  that if  the Company  enters into  similar
agreements  for gene expression with other third  parties, it may be required to
refund a portion of the development funding received from GI and future  funding
may  be proportionately reduced. As a result  of the agreement entered into with
Incyte in April 1996, the Company expects to refund a portion of such funding to
GI  in  1996.  In  addition,  either  party  has  the  right  to  terminate  the
collaboration  for lack of feasibility or  if the parties cannot reach agreement
on certain matters, in which event the  Company could be obligated to refund  up
to 50% of the funding paid by GI.
 
    Until  five years from the end of the research collaboration, Affymetrix has
agreed to  supply  custom  probe  arrays  to GI  for  gene  discovery  and  gene
expression  research  in  certain  designated  fields  in  return  for specified
payments. In addition,  upon the  achievement of technical  milestones, GI  pays
Affymetrix  milestone payments. Until November  1999, the Company cannot develop
probe arrays duplicating  specific characteristics  of those  developed for  GI.
Thereafter,  the Company can sell  such probe arrays, provided  that they do not
contain proprietary sequences or other confidential information belonging to GI.
GI will have all rights to therapeutic
 
                                       40
<PAGE>
compounds discovered through the use of DNA probes provided by the Company,  and
the  Company will receive  royalties on certain  such therapeutic compounds. The
Company retains all  rights to  enhancements to the  GeneChip system  technology
developed in the collaboration.
 
    In December 1995, the Company and GI expanded their relationship by entering
into  a supply agreement in  the field of genomics  under which the Company will
manufacture and supply additional  custom probe arrays  based on specific  genes
identified and selected by GI. Unlike the 1994 agreement with GI, this agreement
does  not provide research funding to the Company. Pursuant to the agreement, GI
is obligated to purchase and the Company is obligated to supply certain  minimum
quantities  of the custom probe arrays developed  for GI until the later of 2001
or four years  after development  of specified  probe arrays.  The Company  will
receive  fees for the design and delivery of the custom probe arrays, as well as
certain milestone  payments  and  royalties on  most  therapeutic  compounds  if
developed  by GI using these  probe arrays. GI has  exclusive rights to specific
probe arrays supplied by the Company.
 
    As of March 31, 1996, the Company had received a total of $1.8 million  from
GI, a portion of which is subject to refund.
 
  HEWLETT-PACKARD COMPANY
 
    In November 1994, the Company entered into a collaborative agreement with HP
to combine the Company's GeneChip technology and HP's measurement and instrument
capabilities  to develop  and manufacture a  more advanced scanner  for use with
GeneChip probe arrays.
 
    Pursuant to the agreement,  the Company will  develop and manufacture  probe
arrays  and HP will develop and manufacture instruments to read the arrays. Each
of the parties is obligated to supply the components of the system developed  by
it  to the other party.  Under certain circumstances, if  either party ceases to
supply its component, the other party  could obtain the manufacturing rights  to
such component.
 
    The agreement also specifies marketing rights outside of the clinical market
in  certain non-clinical  fields. HP has  primary rights to  market the GeneChip
system to the bioanalytical market, and the Company has primary rights to market
the GeneChip system in the biomedical research market. The Company has rights to
market the system for clinical use, subject to HP's option to certain rights  in
selected clinical markets. The Company also has reserved rights to supply custom
probe arrays for collaborations in the genomics field.
 
    As  of March 31, 1996, the Company had received a total of $3.0 million from
HP under this collaboration,  consisting of research  funding, license fees  and
option  payments.  The Company  is also  entitled  to receive  certain milestone
payments and royalties on HP's sales of  the GeneChip system and HP is  entitled
to  receive royalties on any  systems sold by the  Company. The collaboration is
for  a  five-year  term  and  is  renewable  for  consecutive  three-year  terms
thereafter, subject to either party's right to terminate on six months notice.
 
    Pursuant  to  the agreement,  the Company,  in  collaboration with  HP, will
manufacture and supply a limited number of custom probe array designs for HP  in
the nonclinical field. HP also has a one-year option, to sponsor the development
of  custom  probe arrays  in certain  specified fields  and to  obtain exclusive
rights to such probe  arrays. In the  event that HP  exercises such option,  the
Company  will be required to develop the probe  arrays on a timely basis. If the
Company fails to  provide the  requested probe arrays,  it will  be required  to
grant  HP rights to  develop and manufacture  such probe arrays,  subject to the
payment of established royalty rates to the Company.
 
  ADVANCED TECHNOLOGY PROGRAM (UNITED STATES DEPARTMENT OF COMMERCE)
 
    In October 1994,  the Company and  Molecular Dynamics were  awarded a  $31.5
million  five-year grant to develop novel point-of-care diagnostic systems under
the  National  Institute  of  Standards  and  Technology's  Advanced  Technology
Program.  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
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.  The  research
agreements  between the Company and its  subcontractors under the ATP grant (the
University of
 
                                       41
<PAGE>
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 March 31, 1996, the Company had received $1.4 million under the ATP grant.
The grant is subject to yearly appropriations by the United States Congress  for
the  ATP program, and legislation has  been introduced to eliminate the 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 received a  three-year grant for approximately
$6.0 million  from the  NIH National  Center for  Human Genome  Research, for  a
project  entitled  "Sequencing and  Mapping with  DNA  Probe Arrays."  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. The  Company has  been awarded  approximately $2.0  million for  the
first  year  of the  grant,  and the  remaining  amounts are  subject  to yearly
appropriations by the NIH. There  can be no assurance  that the NIH will  obtain
the  necessary funding from the United States  Congress to continue to fund this
grant.
 
  OTHER AGREEMENTS
 
    The Company has agreements with several  entities to develop and test  probe
arrays  for the  detection of  certain gene  sequences, mutations  or organisms.
These include a  one-year feasibility  agreement with  Roche Molecular  Systems,
Inc.,  entered  into  in  November  1995,  for  detection  of  certain mutations
associated with  the  cystic fibrosis  transmembrane  regulator (CFTR)  gene,  a
six-month  feasibility  agreement with  Incyte, entered  into  in April  1996 to
evaluate the use of  DNA probe arrays  to generate gene  expression data, and  a
development  and  supply  agreement entered  into  in  May 1996  with  Glaxo for
detection of polymorphisms in specific  genes, which has a  term of up to  three
years.  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. For  example,  the Company  has  an agreement  with  Dr.  Francis
Collins  at  the NIH  for  the development  of  probe arrays  to  detect certain
mutations believed to be associated with  the development of breast cancer,  and
an  agreement with  Dr. Eric  Lander at  the Whitehead  Institute for Biomedical
Research at  MIT  to  collaborate  in the  investigation  of  single  nucleotide
polymorphism markers using DNA probe arrays.
 
    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. 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.  There can  be no  assurance that  the Company  will be  able to
maintain its  current collaborations,  negotiate collaborative  arrangements  on
acceptable terms, if at all, or that any collaborations will be successful.
 
INTELLECTUAL PROPERTY
 
    As  of April  15, 1996, Affymetrix  had exclusive licenses  from Affymax for
over 20 patents  and patent  applications in the  United States  related to  its
business in the fields of clinical diagnostics and research supply. In addition,
Affymetrix  is  the assignee  of 52  United States  patent applications  and one
issued patent in the United States. 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
 
                                       42
<PAGE>
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 copyright and
trade secrets and to operate without infringing the proprietary rights of  third
parties.
 
    In  1993 Affymetrix and Affymax entered  into a technology license agreement
(the "Technology  License  Agreement")  pursuant to  which  Affymax  granted  to
Affymetrix   an  exclusive,  worldwide,  royalty-free   license  with  right  to
sublicense, among other things, certain patents and patent applications (and any
foreign counterparts) to develop,  make, use and sell  certain products for  the
clinical  diagnostic and research  supply markets, including  rights to sell DNA
probe  arrays.  The  patents  licensed  to  Affymetrix  include  those  for  the
light-directed   synthesis  technology  and   for  several  other  technologies.
Affymetrix has the exclusive  right to sell DNA  probe array technology for  DNA
sequencing and sequence analysis. The Company's rights to the other technologies
are for the fields of diagnostics and analytical and bioanalytical tests, and do
not include other fields such as drug discovery. In addition, Affymax granted to
Affymetrix an exclusive license to certain trademarks, including "Affymetrix."
 
    Pursuant  to  the  Technology  License Agreement,  Affymax  also  granted to
Affymetrix certain rights to future inventions made by, or on behalf of, Affymax
to use such inventions for the development and commercialization of, among other
things, certain  products  in  the  clinical  diagnostics  and  research  supply
markets,  including rights  to sell  DNA probe  arrays. These  rights consist of
either an exclusive, worldwide royalty-free license with right to sublicense  or
a  right of  first negotiation covering  such inventions made  during the period
until July 2000. In turn, Affymetrix granted to Affymax certain parallel  rights
to future inventions made by, or on behalf of, Affymetrix during the same period
for  the development  and commercialization  of products  in drug  discovery and
related fields, not including those related to DNA sequence analysis. The rights
granted to Affymax consist of an exclusive, worldwide royalty-free license  with
right  to sublicense, to develop and commercialize any new Affymetrix technology
that is  dominated  by  one or  more  patents  licensed to  Affymetrix  in  drug
discovery and related fields, and the right of first negotiation with respect to
other  Affymetrix inventions in these fields, not including those related to DNA
sequence analysis. In addition, Affymetrix  agreed to notify Affymax in  advance
of  its intention  to sell  certain products  in the  research supply  market to
ensure that such products cannot be used for drug discovery, as reagents for  IN
VIVO imaging or certain other related purposes.
 
    The Company is party to various license option agreements with third parties
(including  Stanford University 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 technology under  commercially
reasonable  terms could have an adverse effect  on the ability of the Company to
sell certain of its products.
 
    The patent positions of pharmaceutical, biopharmaceutical 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  if it is  required 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, and there is
no assurance such a license will be available on commercially reasonable  terms.
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
 
                                       43
<PAGE>
scanners,   synthesis  techniques,   oligonucleotide  amplification  techniques,
assays, and probe arrays. There  can be no assurance  that the Company will  not
infringe on these patents, other patents or proprietary rights of third parties.
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.  Any  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 partner  to  obtain a  license  in order  to  continue to
manufacture or  market the  affected products  and processes.  There can  be  no
assurance  that the Company  or its collaborative partners  would prevail in any
such action or that any license  (including licenses proposed by third  parties)
required  under  any  such  patent  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. If the Company  becomes
involved  in  such litigation,  it could  consume a  substantial portion  of the
Company's managerial  and  financial  resources, which  could  have  a  material
adverse  effect on  the Company's business,  financial condition  and results of
operations.
 
    Others may  have  filed  and  in  the  future  are  likely  to  file  patent
applications that are similar or identical to those of the Company. 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 meaningly 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.
 
COMPETITION
 
    Competition in genomics and diagnostics is intense and expected to increase.
Further,  the  technologies for  discovering  genes 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, Boehringer Mannheim GmbH, Roche, 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  field,  competitive  technologies include  gel-based  sequencing using
instruments provided by companies such as the
 
                                       44
<PAGE>
Applied Biosystems division of Perkin Elmer  and Pharmacia Biotech AB. 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.
 
    The  market for diagnostic 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 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.
 
    In the genomics  field, future  competition 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, Human Genome
Sciences, Inc., Incyte, Millenium  Pharmaceuticals, Inc., Myriad Genetics,  Inc.
and  Sequana Therapeutics, Inc.  have significant needs  for genomic information
and may choose to develop or acquire competing technologies to meet these needs.
 
GOVERNMENT REGULATION
 
    The Company anticipates that  the manufacturing, labeling, distribution  and
marketing of some or all of the Company's diagnostic products will be 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  analytes, and,  using  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  recently
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 will 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 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 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).
 
                                       45
<PAGE>
    There can be no assurance  that the Company 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.
 
    Medical  device manufacturers are subject to periodic inspections by the FDA
and state agencies. Additionally, 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 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
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.
Medical  device laws and regulations are also  in effect in some states in which
the Company  does business.  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.
 
    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 is currently considering significant changes to its GMP and 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 the 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
 
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<PAGE>
diagnostic products.  Therefore,  there  can  be  no  assurance  that  the  CLIA
regulations  and future administrative  interpretations of CLIA  will not have a
material adverse impact on the Company 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  and  disposal  of  hazardous
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  Company's ability to successfully commercialize its products may depend
on the Company's ability to obtain adequate levels of third-party  reimbursement
for  use of certain diagnostic  tests, in the United  States, European and other
countries. Currently, the availability  of third-party reimbursement is  limited
and uncertain for genetic tests.
 
    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 device or diagnostic test  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 Company's  ability
to  commercialize certain of its products  successfully may depend on the extent
to which appropriate  reimbursement levels for  the costs of  such products  and
related  treatment  are  obtained from  government  authorities,  private health
insurers  and  other  organizations,  such  as  HMOs.  Third-party  payors   are
increasingly  challenging the prices charged  for medical 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 services  and  products,  as  well  as
legislative  proposals  to reform  health  care or  reduce  government insurance
programs, may all result in lower prices for certain of the Company's  products.
The cost containment measures that health care providers are instituting and the
impact  of any health care reform could  have an adverse effect on the Company's
ability to sell certain of its products  and may have a material adverse  effect
on the Company's business, financial condition and results of operations.
 
EMPLOYEES
 
    As  of March 31,  1996, Affymetrix had  117 full-time employees,  29 of whom
hold Ph.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  or
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 its relations with its employees are good.
 
FACILITIES
 
    Affymetrix subleases  47,000 square  feet in  Santa Clara,  California  from
Affymax  for  research laboratories  and  administrative offices  under  a lease
expiring in 1996. The Company has an option to renew the lease on this  facility
for  an additional seven 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 to its  existing facilities over the next few years.
See "Certain Transactions."
 
LEGAL PROCEEDINGS
 
    The Company is not a party to any legal proceedings.
 
SCIENTIFIC ADVISORY BOARD
 
    The Company's scientific advisors have made significant contributions to the
development of Affymetrix technologies.  Each scientific advisor spends  between
one day per week and one day per quarter working on Company projects. Scientific
advisors  are compensated on  a retainer or  per diem basis  and have options to
acquire Common Stock of the Company subject to vesting during continued service.
 
                                       47
<PAGE>
    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.
 
    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 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,  and
point mutational analysis.
 
    ERIC  LANDER, D. PHIL., is a  director of 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 serves
as  Chair of  the Genome  Research Review Committee  of the  National Center for
Human Genome  Research. 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  involved  in artificial
intelligence programs and has served on the Advisory Health Research Council  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.
 
    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 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. He is a director  of
Tencor  Instruments and Park Scientific  Instruments. 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).
 
    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.
 
                                       48
<PAGE>
                                   MANAGEMENT
 
EXECUTIVE OFFICERS AND DIRECTORS
    The executive officers and  directors of the Company,  and their ages as  of
March 31, 1996, are as follows:
 
<TABLE>
<CAPTION>
                   NAME                         AGE                                 POSITION
- ------------------------------------------      ---      ---------------------------------------------------------------
<S>                                         <C>          <C>
John D. Diekman...........................          53   Chairman and Chief Executive Officer
Stephen P.A. Fodor........................          42   President, Chief Operating Officer and Director
Paul M. Kaplan............................          50   Vice President of Product Development
Vernon A. Norviel.........................          37   Vice President and General Counsel
Kenneth J. Nussbacher.....................          43   Executive Vice President and Chief Financial Officer
Richard P. Rava...........................          38   Vice President of Research and Engineering
Paul Berg (1).............................          69   Director
Douglas M. Hurt (2).......................          39   Director
Vernon R. Loucks, Jr......................          61   Director
Barry C. Ross.............................          47   Director
David B. Singer (2).......................          33   Director
John A. Young (1)(2)......................          64   Director
Alejandro C. Zaffaroni (1)................          73   Director
</TABLE>
 
- ------------
(1) Member of the Compensation Committee
 
(2) Member of the Audit Committee
 
    JOHN D. DIEKMAN, PH.D., has served as a Director of the Company and Chairman
since  the Company's inception and was appointed Chief Executive Officer in July
1995. 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. Prior  to 1991, Dr. Diekman served as President  of
Monoclonal  Antibodies Inc. (now  Quidel Corp.), a  diagnostic products company;
Salutar, Inc.,  an  IN VITRO  diagnostic  company; and  Zoecon  Corporation,  an
agrochemical  company. Dr. Diekman also currently serves as a director of Quidel
Corp.
 
    STEPHEN P.A. FODOR, PH.D., is the  President and Chief Operating Officer  of
the  Company and has  been a Director  of the Company  since February 1993. From
September 1994 to July 1995, he served 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.   For  the  invention  of  the
photolithographic synthesis technology  used by the  Company to manufacture  its
probe  arrays,  Dr.  Fodor  and  his  colleagues  were  awarded  the  1992  AAAS
Newcomb-Cleveland Prize for the best  research article published in SCIENCE  and
the  1993 "Distinguished Inventor Award"  from the Intellectual Property Owners'
Association.
 
    PAUL M. KAPLAN, PH.D., has been Vice President of Product Development  since
joining  the Company in April 1994. From 1988 to 1994, Dr. Kaplan served as Vice
President, Research  and Development  of the  Diagnostic Division  at  Centocor,
Inc.,   where  he  was  responsible  for  the  identification,  development  and
commercialization of a variety of proprietary immunoassay products.
 
    VERNON A. NORVIEL, J.D., was appointed Vice President and General Counsel of
the Company in February 1996. From 1989 to 1996, as a partner with Townsend  and
Townsend  and Crew LLP  ("Townsend"), Mr. Norviel  led the intellectual property
and patent  prosecution efforts  of  the Company.  Mr.  Norviel continues  as  a
partner with Townsend on a part time basis.
 
    KENNETH  J.  NUSSBACHER,  J.D.,  joined the  Company  in  September  1995 as
Executive Vice President  and Chief Financial  Officer. From 1989  to 1995,  Mr.
Nussbacher    held    various    management   positions    at    Affymax,   most
 
                                       49
<PAGE>
recently as Executive Vice President for Business and Legal Affairs and Managing
Director of Affymax Technologies  N.V. Prior to  1989, Mr. Nussbacher  practiced
intellectual  property law  in the high  technology field as  General Counsel of
Daisy Systems, as  Vice President,  Intellectual Property for  Atari, Inc.,  and
with Kirkland & Ellis, in Chicago.
 
    RICHARD  P.  RAVA,  PH.D., has  served  as  Vice President  of  Research and
Engineering since September 1994. 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. From  1990 to 1992, he was a  Principal
Research  Scientist in the George R. Harrison Spectroscopy Laboratory at MIT and
the research coordinator for the NIH Laser Biomedical Research Center at MIT.
 
    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 1989-93 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.
 
    JOHN A. YOUNG, a Director of the  Company since August 1993, is the  retired
President  and Chief  Executive Officer  of Hewlett-Packard  Co. Mr.  Young also
serves as a director of Wells Fargo & Company, Chevron Corp., SmithKline Beecham
Corp., Novell, Inc., Ciphergen  Bio Systems, Inc.,  General Magic, Inc.,  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 Affymax, ALZA
Corporation ("ALZA"), DNAX Research Institute  of Molecular & Cellular  Biology,
Inc.  and a co-founder  of Syntex. 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.
 
BOARD OF DIRECTORS COMMITTEES AND OTHER INFORMATION
 
    All  directors are  elected at the  annual meeting of  shareholders and hold
office until the  election and  qualification of  their successors  at the  next
annual  meeting of shareholders. Officers of the Company serve at the discretion
of the Board of Directors. There are no family relationships among the Company's
directors and executive officers.
 
    The Board of Directors currently has  an Audit Committee and a  Compensation
Committee.  The  Audit Committee  oversees the  actions  taken by  the Company's
independent auditors and reviews the Company's
 
                                       50
<PAGE>
internal financial  and  accounting  controls  and  policies.  The  Compensation
Committee is responsible for determining salaries, incentives and other forms of
compensation  for officers  and other employees  of the  Company and administers
various incentive compensation and benefit plans.
 
DIRECTOR COMPENSATION
 
    During the fiscal year  ending December 31, 1995,  John D. Diekman,  Stephen
P.A.  Fodor and David  B. Singer received the  cash compensation described under
"Management -- Executive Compensation." During the same fiscal year each of  the
remaining  directors received a cash payment of $2,500 for each meeting attended
plus reasonable expenses. In December  1995, each nonemployee director  received
an  option to purchase 33,333  shares of Common Stock  at $0.675 per share under
the Company's Stock Plan.
 
COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION
 
    The  Compensation  Committee  is   responsible  for  determining   salaries,
incentives  and other forms of compensation  for officers and other employees of
the Company and  administers various incentive  compensation and benefit  plans.
The Compensation Committee consists of Paul Berg, John A. Young and Alejandro C.
Zaffaroni.  Stephen P.A.  Fodor, President  and Chief  Operating Officer  of the
Company, participates in  all discussions and  decisions regarding salaries  and
incentive  compensation for all employees and consultants of the Company, except
that Dr.  Fodor  is excluded  from  discussions  regarding his  own  salary  and
incentive compensation.
 
EXECUTIVE COMPENSATION
 
    The  following table sets forth certain  compensation paid by the Company in
the year  ended December  31, 1995  to the  Company's Chief  Executive  Officer,
former  Chief Executive Officer,  and to the  Company's other executive officers
who earned in excess of $100,000 (collectively, the "Named Executive Officers"):
 
                           SUMMARY COMPENSATION TABLE
 
<TABLE>
<CAPTION>
                                                                                        LONG-TERM
                                                                                      COMPENSATION
                                                                                         AWARDS
                                                                                      -------------
                                                               ANNUAL COMPENSATION     SECURITIES
                                                             -----------------------   UNDERLYING      ALL OTHER
NAME AND PRINCIPAL POSITION                                     SALARY       BONUS       OPTIONS     COMPENSATION
- -----------------------------------------------------------  ------------  ---------  -------------  -------------
<S>                                                          <C>           <C>        <C>            <C>
John D. Diekman
 Chief Executive Officer and Chairman......................  $   97,304(1) $  --          166,666     $   --
David B. Singer
 Former President and Chief Executive Officer..............     183,010       --           33,333         6,189
Stephen P.A. Fodor
 President and Chief Operating Officer.....................     188,819       --          166,666         --
Paul M. Kaplan
 Vice President of Product Development.....................     146,218       --           26,666        33,638(2)
Richard P. Rava
 Vice President of Research and Engineering................     136,962       --           60,000         --
</TABLE>
 
- ------------
(1) Represents Dr.  Diekman's  compensation commencing  July  1, 1995,  when  he
    joined the Company. Prior to March 1996 when he became a full-time employee,
    Dr. Diekman devoted 80% of his time to the Company and 20% to Affymax.
 
(2) Includes  reimbursement  for  certain  relocation  expenses  of  $21,556 and
    housing allowances of $12,082.
 
                                       51
<PAGE>
STOCK OPTION GRANTS
 
    The  following table contains information concerning the stock option grants
made to each of  the Named Executive  Officers for the  year ended December  31,
1995:
 
                 OPTION GRANTS IN YEAR ENDED DECEMBER 31, 1995
 
<TABLE>
<CAPTION>
                                                  INDIVIDUAL GRANTS
                              ---------------------------------------------------------  POTENTIAL REALIZABLE VALUE
                                NUMBER OF                                                AT ASSUMED ANNUAL RATES OF
                               SECURITIES      % OF TOTAL                                 STOCK PRICE APPRECIATION
                               UNDERLYING    OPTIONS GRANTED    EXERCISE                    FOR OPTION TERMS (1)
                                 OPTIONS     TO EMPLOYEES IN    PRICE PER    EXPIRATION  --------------------------
NAME                           GRANTED (2)     FISCAL YEAR        SHARE         DATE          5%           10%
- ----------------------------  -------------  ---------------  -------------  ----------  ------------  ------------
<S>                           <C>            <C>              <C>            <C>         <C>           <C>
John D. Diekman.............      100,000            9.7%       $   0.675     07/01/05   $  1,887,300  $  3,045,300
                                   66,666            6.5            0.675     12/20/05      1,258,200     2,030,200
David B. Singer.............       33,333            3.2            0.675     12/20/05        629,100     1,015,100
Stephen P.A. Fodor..........      166,666           16.2            0.675     12/20/05      3,145,500     5,075,500
Paul M. Kaplan..............       26,666            2.6            0.675     12/20/05        503,300       812,100
Richard P. Rava.............       60,000            5.8            0.675     12/20/05      1,132,400     1,827,200
</TABLE>
 
- ------------
(1) Assumes a value of $12.00 for each share of Common Stock (the initial public
    offering  price for this offering) on the date of grant. Potential gains are
    net of the exercise price but before taxes associated with the exercise. The
    5% and  10%  assumed  annual  rates of  compounded  stock  appreciation  are
    mandated  by the rules of the Securities  and Exchange Commission and do not
    represent the Company's estimate  or projection of  the future Common  Stock
    price.  Actual gains, if any, on stock option exercises are dependent on the
    future financial performance of the  Company, overall market conditions  and
    the option holders' continued employment through the vesting period.
 
(2)  Grants generally  vest at  a rate of  20% each  year following  the date of
    grant, as long as the optionee  remains an employee with, consultant to,  or
    director  of, the Company.  The maximum term  of each option  granted is ten
    years from the date of grant. The exercise price is equal to the fair market
    value of  the  stock  on the  grant  date  as determined  by  the  Board  of
    Directors.
 
    The  following table  sets forth  for each  of the  Named Executive Officers
certain information with respect to the  exercise of options to purchase  Common
Stock  during the year ended December 31,  1995 and the number of shares subject
to both exercisable and unexercisable stock options as of December 31, 1995.
 
    AGGREGATE OPTION EXERCISES IN FISCAL YEAR-END AND FISCAL YEAR-END VALUES
 
<TABLE>
<CAPTION>
                                                        NUMBER OF SECURITIES
                                                       UNDERLYING UNEXERCISED     VALUE OF UNEXERCISED IN-
                                                             OPTIONS AT             THE-MONEY OPTIONS AT
                             SHARES                      DECEMBER 31, 1995         DECEMBER 31, 1995 (1)
                           ACQUIRED ON     VALUE     --------------------------  --------------------------
NAME                        EXERCISE    REALIZED (2) EXERCISABLE  UNEXERCISABLE  EXERCISABLE  UNEXERCISABLE
- -------------------------  -----------  -----------  -----------  -------------  -----------  -------------
<S>                        <C>          <C>          <C>          <C>            <C>          <C>
John D. Diekman..........      --           --           --           166,666        --        $ 1,887,500
David B. Singer..........      --           --           50,000        33,333     $ 566,200        377,500
Stephen P.A. Fodor.......      --           --           20,000       246,666       226,500      2,793,500
Paul M. Kaplan...........      --           --            8,000        58,666        92,600        672,000
Richard P. Rava..........      10,000    $   3,750        1,333        88,666        15,000      1,013,000
</TABLE>
 
- ------------
(1) Based on an  assumed initial offering  price of $12.00  per share minus  the
    exercise price.
 
(2) Based on the fair market value at the date of exercise, as determined by the
    Board of Directors, minus the exercise price.
 
                                       52
<PAGE>
STOCK PLANS
 
  1993 STOCK PLAN
 
    The  Company's Stock Plan was adopted by  the Board of Directors in February
1993, approved  by the  shareholders  in July  1993  and has  been  subsequently
amended.  As of March 31, 1996, a total of 3,700,000 shares of Common Stock have
been reserved for issuance under the Stock  Plan. As of March 31, 1996,  options
to  purchase a total  of 543,254 shares  of Common Stock  had been exercised (of
which 148,889 are subject to repurchase  by the Company), options to purchase  a
total  of 2,191,518  shares at  a weighted average  exercise price  of $0.65 per
share were outstanding, and 965,228 shares remain available for future option or
purchase rights grants.
 
    The purpose of the Stock Plan  is to attract, retain and motivate  officers,
key  employees,  consultants and  directors of  the Company  by giving  them the
opportunity to acquire Stock ownership in  the Company. The Stock Plan  provides
for  the granting to  employees of the Company  (including officers and employee
directors) of "incentive stock options" within the meaning of Section 422 of the
Code, for the grant of nonstatutory  stock options to employees and  consultants
of  the Company, and for  the grant of purchase  rights providing for the direct
sale of  stock to  eligible participants,  subject to  the Company's  repurchase
rights.  To the extent an optionee would have  the right in any calendar year to
exercise for  the  first time  incentive  stock  options for  shares  having  an
aggregate  fair market value (under all plans  of the Company and determined for
each share as of the grant date) in excess of $100,000, any such excess  options
shall be automatically converted to a nonstatutory stock option.
 
    The  Stock Plan is administered by the  Board of Directors or a committee of
the Board of Directors (the  "Administrator"). The Administrator determines  the
type  and terms  of options  and purchase rights  granted under  the Stock Plan,
including the number  of shares covered,  exercise or purchase  price, term  and
condition  for exercise of the  option or purchase right.  The exercise price of
all stock options granted under  the Stock Plan must be  at least 100% (85%  for
purchase  rights) of the fair market value of the Common Stock of the Company on
the grant date. The term of an  incentive stock option may not exceed ten  years
from  the  date  of  grant.  With respect  to  any  participant  who  owns stock
possessing more than  10% of the  voting power of  all classes of  stock of  the
Company,  the exercise price of any stock  option granted shall be at least 110%
(100% for purchase rights) of the fair  market value of the Common Stock on  the
grant date and the term of such option may not exceed five years. Payment of the
exercise   price  may  be  in  cash,  check,   or,  at  the  discretion  of  the
administrator, by promissory notes  or shares of stock  held by the optionee  or
purchaser, or a combination thereof.
 
    No  option may be transferred by the optionee other than by will or the laws
of descent and distribution or pursuant to a qualified domestic relations  order
("QDRO").  During  the  lifetime  of  an optionee,  only  the  optionee  (or the
optionee's spouse pursuant to a QDRO) may exercise an option. An option shall be
exercisable on or after each vesting date in accordance with the terms set forth
in the option agreement; provided, however, that the right to exercise an option
must vest at the rate of  at least 20% per year  over five years from the  grant
date.
 
    In  the event  of certain  changes in control  of the  Company or  a sale of
substantially all  its assets,  the Administrator  may cancel  each  outstanding
option  upon payment in cash to the optionee of the amount by which any cash and
any other property  which the  optionee would have  received for  the shares  of
stock  covered by the vested portion of the option exceeds the exercise price of
the option. The Board may amend, suspend or terminate the Stock Plan as long  as
such  action does not adversely affect  any outstanding option or purchase right
and provided that shareholder  approval shall be required  for any amendment  to
(i)  increase the number  of shares subject  to the Stock  Plan, (ii) materially
change eligibility  for  the grant  of  options  or purchase  rights,  or  (iii)
materially  increase the  benefits accruing  to participants.  If not terminated
earlier, the Stock Plan will terminate in 2003.
 
  1996 NONEMPLOYEE DIRECTORS STOCK OPTION PLAN
 
    The Company's Directors Plan was adopted by the Board of Directors in  March
1996 and approved by the shareholders in April 1996. 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
 
                                       53
<PAGE>
only nonstatutory stock options can be granted. The Directors Plan provides that
option  grants to nonemployee directors  of the Company are  made on a mandatory
basis and not on a discretionary  basis. The Directors Plan may be  administered
by the Board of Directors or the Board may delegate its authority to a committee
composed  of not less  than two outside directors  (the "Administrator") and may
delegate routine matters to management.
 
    If a person who is neither an officer nor an employee of the Company and who
has not previously been a member of the Board is elected or appointed  director,
the  Company  is required  to grant  that  person an  initial 10-year  option to
purchase 33,333 shares of the Company's Common Stock at an exercise price  equal
to  the fair market value of Common Stock on the date of grant. Each such option
will become exercisable at the rate of one-fifth of the number of shares covered
by the option on each anniversary of the  grant date so long as the director  is
serving on the Board with full vesting over five years.
 
    In  addition, on the date of each  annual meeting of the shareholders of the
Company held  after  January 1,  2001  for existing  nonemployee  directors  who
continue  on the Board and after 54 months after the initial option grant to new
nonemployee directors who continue on the Board, the Company will grant to  each
nonemployee director a ten-year option to purchase 6,667 shares of the Company's
Common  Stock, at  an exercise price  equal to  the fair market  value of Common
Stock on the date of grant. These options will vest one year after grant.
 
    The consideration  payable  in connection  with  any option  (including  any
related  taxes)  may be  paid in  cash,  by promissory  note of  the nonemployee
director or  by delivery  of shares  of  Common Stock  of the  Company.  Options
generally  terminate three months after a nonemployee director ceases to be, for
any reason,  a director  of the  Company, with  the following  exceptions: if  a
nonemployee  director  ceases  to be  a  director  due to  death,  disability or
retirement, the option may be exercised for 18 months after the termination.
 
    The Board may amend, alter, or discontinue the Directors Plan or any  option
at  any  time, except  that  the consent  of a  participant  is required  if the
participant's existing rights under an outstanding option would be impaired.  In
addition,  to the extent  required under applicable tax  and securities laws and
regulations, the  shareholders  of  the  Company  must  approve  any  amendment,
alteration,  or discontinuance  of the  Directors Plan  that would  increase the
total number of shares  reserved under the Directors  Plan and in certain  other
circumstances  as the  Board may  deem advisable  to comply  with such  laws and
regulations. In addition, the  provisions of the plan  governing who is  granted
options,  the number of shares  covered by each option,  the exercise price, and
the period of exercisability and the timing of option grants may not be  amended
more  than once  every six  months, other  than for  changes to  comply with the
Internal Revenue Code of 1986 or the Employee Retirement Income Security Act  of
1974.
 
    In the event of a merger, consolidation, sale of all or substantially all of
the Company's assets, or any like occurrence, the options will vest at twice the
rates set forth above.
 
LIMITATION OF DIRECTORS' LIABILITY AND INDEMNIFICATION
 
    The Company's Articles of Incorporation limit the liability of directors for
monetary  damages  to  the  maximum extent  permitted  by  California  law. Such
limitation of liability has no effect on the availability of equitable remedies,
such as injunctive relief or rescission. The Company is also empowered under its
Articles of  Incorporation to  enter into  indemnification agreements  with  its
directors and officers and to purchase insurance on behalf of any person whom it
is  required to  indemnify. The Company's  Bylaws provide that  the Company will
indemnify its  directors  and officers  as  a contractural  obligation  and  may
indemnify  its employees and  agents against certain  liabilities to the fullest
extent permitted by California law. The Company has entered into indemnification
agreements  with  each  of  its  current  directors  and  officers  or   persons
controlling the Company pursuant to the foregoing provisions.
 
                                       54
<PAGE>
                              CERTAIN TRANSACTIONS
 
    In  September 1993,  the Company  sold an  aggregate of  6,000,000 shares of
Series A  Preferred Stock  (the "Series  A") at  $3.50 per  share in  a  private
placement transaction. In August 1995, in another private placement transaction,
the  Company sold an aggregate  of 8,666,666 shares of  Series B Preferred Stock
(the "Series B") at $4.50 per share.
 
    The purchasers of the  Series A and Series  B (collectively, the  "Preferred
Stock")  included, among others, the  following executive officers and directors
of the Company  and investors  known to  own beneficially  more than  5% of  the
Company's  outstanding  Common  Stock (assuming  conversion  of  all outstanding
shares of Preferred Stock into Common Stock) (see "Principal Shareholders"):
<TABLE>
<CAPTION>
                                                                                    NUMBER OF SHARES
                                                                                 ----------------------
DIRECTORS AND EXECUTIVE OFFICERS                                                  SERIES A    SERIES B
- -------------------------------------------------------------------------------  ----------  ----------
<S>                                                                              <C>         <C>
John D. Diekman................................................................      20,000      40,000
Paul A. Berg...................................................................      10,000      15,000
John A. Young..................................................................      20,000      40,000
Vernon R. Loucks, Jr...........................................................      --          40,000
Alejandro C. Zaffaroni.........................................................      --         450,000
 
<CAPTION>
 
5% SHAREHOLDERS
- -------------------------------------------------------------------------------
<S>                                                                              <C>         <C>
Glaxo Wellcome plc (indirectly through Affymax N.V.)...........................   1,250,000   1,333,333
College Retirement Equities Fund...............................................   1,428,570     800,000
R.A. Investment Group..........................................................     570,000     856,000
</TABLE>
 
    In July  1995,  the  Company  and  Glaxo  entered  into  an  agreement  (the
"Governance  Agreement") pursuant  to which Glaxo  has the right  to designate a
number of directors based on the  percentage of voting stock then held  directly
or  indirectly by  Glaxo and is  obligated to vote  its shares for  the slate of
directors recommended  to the  shareholders. Glaxo  currently has  the right  to
designate  four  of  the  nine  directors of  the  Company.  See  "Management --
Executive Officers and Directors." Pursuant  to the Governance Agreement,  Glaxo
also  agreed that any merger, consolidation  or business combination whereby the
Company would become a direct or  indirect wholly-owned subsidiary of Glaxo  and
any  material transaction between  the Company and  Glaxo must be  approved by a
majority of the independent directors of  the Company. In addition, pursuant  to
the  Governance Agreement, the Company granted Glaxo certain registration rights
with respect to its shares. See "Description of Stock -- Registration Rights  of
Certain Shareholders."
 
    In  December 1994,  Affymax provided  a bridge  loan to  the Company  in the
principal amount  of $6.0  million. The  loan was  evidenced by  a  subordinated
convertible  promissory note, the terms of  which were amended by the Governance
Agreement (the "Convertible Note")  and was converted  into 1,333,333 shares  of
Series  B Senior  Convertible Preferred  Stock in  August 1995.  Interest on the
Convertible Note  through the  date of  conversion, amounting  to $319,856,  was
satisfied by the Company issuing Affymax three five-year warrants to purchase an
aggregate of 202,441 shares of Series 2 Subordinated Convertible Preferred Stock
at $5.50 per share.
 
    In  connection  with the  lease agreement  between the  Company and  a third
party, in  December 1994,  Affymax  agreed to  relieve  the Company  of  certain
financial  covenants  and to  guarantee  its obligation  to  the third  party in
exchange for warrants  to purchase Series  2 Subordinated Convertible  Preferred
Stock.  In  December  1994, Affymax  received  a five-year  warrant  to purchase
103,382 shares of Series 2 Subordinated Convertible Preferred Stock at $5.50 per
share pursuant to this agreement.
 
    Effective January 1, 1993, the  Company entered into the Technology  License
Agreement  with Affymax whereby  the Company was  granted an exclusive worldwide
royalty free license  from Affymax,  with the  right to  sublicense, to  certain
technology  and  to certain  future inventions  to be  used in  the development,
production and sale  of products  and services  in the  clinical diagnostic  and
research  supply  markets.  See  "Intellectual Property."  In  August  1993, the
Company agreed  to  issue Affymax  8,500,000  shares of  Series  1  Subordinated
Convertible   Preferred  Stock  as  consideration  for  the  Technology  License
Agreement and funding the Company's operations through September 1993.
 
                                       55
<PAGE>
    The Company and Affymax Research Institute, a subsidiary of Affymax ("ARI"),
entered into a Services Agreement dated  October 1, 1993, pursuant to which  ARI
agreed  to  perform  certain  administrative  and  management  services  for the
Company. For the fiscal year ended December 31, 1995, the Company made  payments
to  ARI in the  aggregate amount of $834,000.  John D. Diekman  is a director of
ARI.
 
    In February 1994, the Company entered into a sublease with Affymax providing
for the Company to sublease facilities in Santa Clara from Affymax until October
1, 1995. The sublease provides for its term to be extended until August 31, 2003
in the event  that, at the  Company's request, Affymax  exercises its option  to
extend  the underlying  lease until  that date.  In April  1995, the  option was
exercised to extend the lease to October 1, 1996.
 
    The Company believes that the agreements  with Affymax are on terms no  less
favorable to the Company than would be obtained from unaffiliated third parties.
 
    In May 1996, the Company entered into an agreement with Glaxo to develop and
supply  probe arrays to detect polymorphisms in specific genes. See "Business --
Genomics Application Areas" and "-- Collaborative Agreements and Grants."
 
    In December 1993, in  connection with grants to  each of Stephen P.A.  Fodor
and  David B.  Singer of rights  to purchase  133,333 shares of  Common Stock at
$0.30 per share,  subject to  repurchase at  the Company's  option, the  Company
entered  into Loan and Pledge Agreements with  each of Dr. Fodor and Mr. Singer.
Pursuant to those  agreements, the Company  lent Dr. Fodor  and Mr. Singer  each
$40,000,  which loans are evidenced by secured promissory notes due in July 1998
or when their employment is terminated. These notes bear interest at the rate of
5.07% per annum. Interest payments  on the notes are  due and payable each  year
until the loan is repaid.
 
    In  November 1994, the Company  agreed to guarantee a  loan in the amount of
$117,000 of Stephen P. A. Fodor.
 
    In June 1995, the Company entered into an agreement with David B. Singer  in
connection  with his assumption of  the position of Vice  Chairman of the Board.
Pursuant to Mr. Singer's transition from President, Chief Executive Officer  and
Chief  Financial  Officer to  Vice  Chairman, Mr.  Singer  continues to  be paid
$14,583 per month and may receive health care coverage until December 15,  1996.
In  addition, pursuant to  the agreement, the Company  relinquished its right to
repurchase any of the 133,333 shares of  Common Stock acquired by Mr. Singer  in
December  1993, amended  the option  to purchase  100,000 shares  granted to Mr.
Singer in December 1994 to  fully vest 50,000 shares  as of September 1995,  and
waived  its right  to demand repayment  of Mr. Singer's  $40,000 promissory note
until July 1998.  Pursuant to the  agreement, Mr. Singer  agreed to continue  to
serve as a Director of the Company if nominated and elected by the shareholders,
to  serve as Vice Chairman  of the Board, and  to provide consulting services to
the Company relating  to the  financing of  the Company,  grants and  government
relations.
 
    The Company and Symyx, Inc. ("Symyx") have entered into a sublease agreement
for  a portion  of the  property leased  to the  Company in  Sunnyvale at market
rates. Kenneth J.  Nussbacher is  a director, and  Alejandro C.  Zaffaroni is  a
director and greater than 10% stockholder, of Symyx.
 
    The  Company has  entered into indemnification  agreements with  each of its
directors and  executive  officers.  Such  agreements  require  the  Company  to
indemnify  such persons to  the fullest extent permitted  by California law. See
"Management -- Limitation of Liability and Indemnification Matters."
 
                                       56
<PAGE>
                             PRINCIPAL SHAREHOLDERS
 
    The following  table sets  forth  certain information  with respect  to  the
beneficial  ownership of the Common Stock as  of April 30, 1996, and as adjusted
to reflect the sale  of the shares  of Common Stock offered  hereby by (i)  each
person who is known by the Company to be the beneficial owner of more than 5% of
the  Common Stock, (ii) each of the Company's directors, (iii) each of the Named
Executive Officers and (iv)  all current directors and  executive officers as  a
group.
 
   
<TABLE>
<CAPTION>
                                                                                               PERCENTAGE OF SHARES
                                                                                                   BENEFICIALLY
                                                                                                   OWNED (1)(2)
                                                                                    SHARES     ---------------------
                                                                                  BENEFICIALLY  PRIOR TO     AFTER
BENEFICIAL OWNER                                                                   OWNED (1)    OFFERING   OFFERING
- --------------------------------------------------------------------------------  -----------  ----------  ---------
<S>                                                                               <C>          <C>         <C>
Glaxo Wellcome plc (3)..........................................................   7,705,067        46.8%      34.3%
Greenford Road
Greenford, Middlesex, UBG OHE, UK
College Retirement Equities Fund................................................   1,507,991         9.3%       6.8%
730 Third Avenue
New York, NY 10017
R.A. Investment Group...........................................................     959,554         5.9%       4.3%
200 West Madison, Suite 3800
Chicago, IL 60606
Paul A. Berg, Ph.D (4)..........................................................      38,488       *           *
John D. Diekman, Ph.D (5).......................................................      76,177       *           *
Stephen P.A. Fodor, Ph.D (6)....................................................     153,333       *           *
Douglas M. Hurt (7).............................................................   7,705,067        46.8 %     34.3%
Paul M. Kaplan (8)..............................................................      13,334       *           *
Vernon R. Loucks, Jr............................................................      59,999       *           *
Richard P. Rava, Ph.D (9).......................................................      11,333       *           *
Barry C. Ross, Ph.D (7).........................................................   7,705,067        46.8 %     34.3%
David B. Singer.................................................................     160,666       *           *
John A. Young...................................................................      41,643       *           *
Alejandro C. Zaffaroni, Ph.D (10)...............................................     140,000       *           *
All directors and executive officers as a group (13 persons) (11)...............   8,426,706        50.9 %     37.4%
</TABLE>
    
 
- ------------
 * Represents beneficial ownership of less than one percent of the Common Stock.
 
 (1)  Beneficial ownership  is determined  in accordance  with the  rules of the
    Securities and  Exchange  Commission.  In computing  the  number  of  Shares
    beneficially  owned  by a  person and  the percentage  of ownership  of that
    person, shares of Common Stock subject  to options held by that person  that
    are  currently exercisable or  exercisable within 60 days  of April 30, 1996
    are deemed outstanding. Such shares, however, are not deemed outstanding for
    the purpose of computing the percentage ownership of each other person.  The
    persons  named  in this  table have  sole voting  and investment  power with
    respect to all shares of Common  Stock shown as beneficially owned by  them,
    subject  to community property laws where applicable and except as indicated
    in the other footnotes to this table.
 
   
 (2) Percentage of beneficial ownership is based on 16,248,148 shares of  Common
    Stock outstanding as of April 30, 1996 and 22,248,148 shares of Common Stock
    outstanding after completion of this offering.
    
 
 (3) Held through its subsidiary, Affymax N.V.  Includes 203,881 shares issuable
    upon exercise of outstanding warrants at $8.25 per share.
 
                                       57
<PAGE>
 (4)  Includes 3,333 shares issuable upon exercise of options exercisable within
    60 days of April 30, 1996.
 
 (5) Includes 40,000 shares issuable upon exercise of options within 60 days  of
    April 30, 1996.
 
 (6)  Includes 20,000 shares issuable upon exercise of options within 60 days of
    April 30, 1996.
 
 (7) Represents 7,705,067 shares beneficially owned by Glaxo, of which Mr.  Hurt
    and Dr. Ross disclaim beneficial ownership.
 
 (8)  Represents  13,334 shares  issuable upon  exercise of  options exercisable
    within 60 days of April 30, 1996.
 
 (9) Includes 1,333 shares issuable upon  exercise of options within 60 days  of
    April 30, 1996.
 
(10)  Includes 6,667 shares issuable upon exercise  of options within 60 days of
    April 30, 1996  and excludes any  shares Dr. Zaffaroni  may purchase in  the
    offering. See "Underwriting."
 
(11)  Includes 98,000 shares issuable upon exercise of options within 60 days of
    April 30, 1996. Also includes 7,705,067 shares owned by Glaxo, of which  Mr.
    Hurt  and Dr.  Ross disclaim beneficial  ownership. Excludes  any shares Dr.
    Zaffaroni may purchase in the offering. See "Underwriting."
 
                                       58
<PAGE>
                          DESCRIPTION OF CAPITAL STOCK
 
    Upon the  closing of  this offering,  the authorized  capital stock  of  the
Company  will consist of  50,000,000 shares of  Common Stock, no  par value, and
27,500,000 shares of Preferred Stock, no par value (the "Undesignated  Preferred
Stock").
 
COMMON STOCK
 
    At  March 31,  1996, assuming  the conversion  of all  outstanding Preferred
Stock and  the  issuance of  203,881  shares of  Common  Stock pursuant  to  the
exercise  or  conversion of  outstanding warrants,  16,443,112 shares  of Common
Stock were outstanding and held of  record by shareholders. Options to  purchase
an  aggregate of  2,191,518 shares  of Common  Stock were  also outstanding. See
"Management -- Stock Plans."
 
    The holders  of Common  Stock are  entitled to  one vote  per share  on  all
matters to be voted upon by the shareholders. Subject to preferences that may be
applicable  to any outstanding Preferred Stock,  the holders of Common Stock are
entitled to receive ratably such dividends, if any, as may be declared from time
to time by the Board of Directors  out of funds legally available therefor.  See
"Dividend  Policy." In the event of a  liquidation, dissolution or winding up of
the Company, the holders of  Common Stock are entitled  to share ratably in  all
assets  remaining  after  payment of  liabilities,  subject to  prior  rights of
Preferred Stock, if any, then outstanding. The Common Stock has no preemptive or
conversion rights  or other  subscription  rights. There  are no  redemption  or
sinking fund provisions available to the Common Stock. All outstanding shares of
Common Stock are fully paid and non-assessable.
 
PREFERRED STOCK
 
    Effective  upon the closing of this offering, the Company will be authorized
to issue  27,500,000  shares  of  Undesignated Preferred  Stock.  The  Board  of
Directors  will have the authority to  issue the Undesignated Preferred Stock in
one or more series and to determine  the powers, preferences and rights and  the
qualifications, limitation or restrictions granted to or imposed upon any wholly
unissued  shares of  Undesignated Preferred Stock  and fix the  number of shares
constituting any series and the designation of such series, without any  further
vote or action by the shareholders. The issuance of Undesignated Preferred Stock
may  have the effect of delaying, deferring or preventing a change in control of
the Company without further action by the shareholders and may adversely  affect
the  voting and  other rights of  the holders  of Common Stock.  At present, the
Company has no plans to issue any shares of Undesignated Preferred Stock.
 
REGISTRATION RIGHTS OF CERTAIN SHAREHOLDERS
 
    Certain holders of Common Stock or their transferees are entitled to certain
rights with respect to the registration of such shares under the Securities Act.
Registration rights are held  with respect to 9,871,185  shares of Common  Stock
issuable  upon the conversion  of Preferred Stock under  the terms of agreements
between the Company and  the holders of  Series A and  B Senior Preferred  Stock
(collectively  the "Registrable Securities"). Subject  to certain limitations in
the agreements, the holders of Registrable Securities have "piggyback" rights to
request that their shares be registered for public resale with respect to up  to
four  registrations  of the  Company's  securities. However,  if  such piggyback
rights are  exercised  in  connection  with  an  underwritten  offering  of  the
Company's Common Stock, the underwriter of such offering has the right to reduce
to  20% of the  total the number  of such shares  to be included  in such public
offering or, in the case of the initial public offering, to exclude such  shares
entirely.  In  addition, at  a time  when  the Company  is eligible  to register
securities on Form S-3, holders of Registrable Securities not already registered
may demand  that  the Company  file  a Form  S-3,  provided that  the  aggregate
offering  price of the Registrable Securities  would be at least $2,000,000. The
Company will  pay  certain expenses  in  connection  with the  exercise  of  the
foregoing  rights. These registration rights expire  five years after an initial
public offering of the Company's securities.
 
    Pursuant to the Governance Agreement, the Company also has granted to Glaxo,
as long as  Glaxo and its  subsidiaries hold  more than 10%  of the  outstanding
Common  Stock of the Company, the right to  demand, at any time after six months
following the  Company's  initial public  offering,  that the  Company  file  an
underwritten registration statement covering the registration of at least 40% of
the Common Stock held by Glaxo and its subsidiaries. Glaxo's registration rights
cover 7,705,067 shares of Common Stock issuable on conversion of Preferred Stock
(including Series 1 Subordinated Convertible Preferred and Series 2 Subordinated
Convertible
 
                                       59
<PAGE>
Preferred  Stock, issuable  upon exercise of  warrants). If such  demand is made
after the time the Company is, or normally would have been, eligible to register
securities on Form S-3, the Company will pay certain expenses incurred by  Glaxo
in  exercising these demand rights. Glaxo has  this demand right with respect to
up to  four  registrations  of the  Company's  securities  on Form  S-1  and  an
unlimited  number of  registrations on  Form S-3.  In addition,  pursuant to the
Governance Agreement,  Glaxo  has piggyback  rights  similar to  those  held  by
holders of the Registrable Securities.
 
WARRANTS
 
    Pursuant  to the terms of an  agreement between Affymetrix and Affymax dated
December 29,  1994,  whereby  Affymax  agreed  to  guarantee  Affymetrix'  lease
obligations  to a  third party,  Affymetrix has issued  to Affymax  a warrant to
purchase 103,382 shares  of Series 2  Subordinated Convertible Preferred  Stock.
The  warrants  have an  exercise price  of  $5.50 and  expire in  December 1999.
Pursuant to the  terms of  a note agreement,  Affymetrix has  issued to  Affymax
warrants  to  purchase  202,441  shares  of  Series  2  Subordinated Convertible
Preferred Stock for certain interest payments otherwise due on the note  through
August  1995, at which time  the note was converted  into Preferred Stock. These
warrants have an exercise  price of $5.50  and expire from  March to July  2000.
After  the offering, as a result of  automatic conversion of the Preferred Stock
upon the closing  of this offering  and the 2-for-3  reverse stock split,  these
warrants will be exercisable for a total of 203,881 shares of Common Stock at an
exercise price of $8.25 per share. See "Certain Transactions."
 
TRANSFER AGENT AND REGISTRAR
 
    The  Transfer Agent and Registrar for the Company's Common Stock is American
Stock Transfer & Trust Company.
 
                                       60
<PAGE>
                        SHARES ELIGIBLE FOR FUTURE SALE
 
   
    Upon  completion  of  this  offering,  the  Company  will  have  outstanding
22,239,231 shares of Common Stock. Of these shares, the 6,000,000 shares sold in
this  offering  (plus  any  shares issued  upon  exercise  of  the Underwriters'
over-allotment option) will  be freely tradeable  without restriction under  the
Securities  Act, unless purchased or held by "affiliates" of the Company as that
term is  defined  in Rule  144  under the  Securities  Act and  the  regulations
promulgated thereunder.
    
 
    The  remaining  16,239,231  shares  of  Common  Stock  outstanding  (or  any
securities exercisable for or convertible into the Company's Common Stock)  held
by  officers, directors,  employees, consultants  and certain  shareholders, are
"restricted securities" within the meaning of Rule 144 under the Securities  Act
("Restricted  Shares"). Restricted Shares may be  sold in the public market only
if registered or if they qualify for an exemption from registration under  Rules
144,  144(k) or 701  promulgated under the Securities  Act, which are summarized
below. Sales of the Restricted Shares in the public market, or the  availability
of  such shares for sale, could adversely  affect the market price of the Common
Stock. None  of  the Restricted  Shares  will be  available  for sale  upon  the
Effective  Date. Approximately  50,100 of these  shares of Common  Stock will be
eligible for sale in the public market 90 days after the Effective Date  subject
to the provisions of Rule 701. In addition, an additional 186,140 shares subject
to  vested options will be  available for sale 90  days after the Effective Date
subject to compliance with Rule 701.
 
    The officers, directors, certain employees  and shareholders of the  Company
have entered into contractual "lock-up" agreements generally providing that they
will  not  offer, sell,  contract to  sell or  grant any  option to  purchase or
otherwise dispose of the shares of Common Stock of the Company or any securities
exercisable for or convertible into the Company's Common Stock owned by them for
a period of 180 days after the Effective Date without the prior written  consent
of  Robertson, Stephens  & Company.  Pursuant to the  Stock Plan,  all shares of
Common Stock  issued upon  exercise of  options are  also subject  to a  lock-up
arrangement  for  a  period of  180  days  after the  date  of  this prospectus.
Robertson, Stephens  & Company  may, in  its  sole discretion  and at  any  time
without  notice, release all or any portion of the securities subject to lock-up
agreements.
 
    As a  result of  these  contractual restrictions,  notwithstanding  possible
earlier  eligibility for sale under the provisions of Rules 144, 144(k) and 701,
shares subject to lock-up agreements will not be saleable until such  agreements
expire  or are waived by Robertson, Stephens & Company. Beginning 180 days after
the Effective Date, approximately  10,411,408 additional Restricted Shares  will
become  eligible for sale subject to the provisions of Rule 144 or Rule 701 upon
the expiration of the lock-up agreements  not to sell such shares. In  addition,
beginning  180  days  after the  Effective  Date, an  additional  183,366 shares
subject to vested options will be available for sale subject to compliance  with
Rule  701 upon  the expiration  of lock-up agreements  not to  sell such shares.
Robertson, Stephens  & Company  may, in  its  sole discretion  and at  any  time
without  notice, release all or any portion of the securities subject to lock-up
agreements.
 
   
    In general, under Rule 144, as currently in effect, beginning 90 days  after
the  Effective Date, a person  (or persons whose shares  are aggregated) who has
beneficially owned Restricted Shares for at least two years would be entitled to
sell within any three-month period a number  of shares that does not exceed  the
greater  of:  (i) one  percent  of the  number of  shares  of Common  Stock then
outstanding (which  will equal  approximately 222,392  shares immediately  after
this  offering); or (ii) the  average weekly trading volume  of the Common Stock
during the four calendar weeks preceding the  filing of a Form 144 with  respect
to  such sale. Sales under  Rule 144 are also subject  to certain manner of sale
provisions and notice  requirements and  to the availability  of current  public
information  about the Company. Under Rule 144(k), a person who is not deemed to
have been an affiliate of the Company at any time during the 90 days preceding a
sale, and who has beneficially owned the shares proposed to be sold for at least
three years, is entitled to sell  such shares without complying with the  manner
of sale, public information, volume limitation or notice provisions of Rule 144.
    
 
    Beginning  90  days after  the Effective  Date,  certain shares  issued upon
exercise of options granted by the Company prior to the date of this  Prospectus
will  also be available for sale in the public market pursuant to Rule 701 under
the Securities Act. Any  employee, officer or director  of or consultant to  the
Company  who purchased his or her shares pursuant to a written compensatory plan
or contract may be entitled to rely  on the resale provisions of Rule 701.  Rule
701  permits affiliates  to sell  their Rule 701  shares under  Rule 144 without
 
                                       61
<PAGE>
complying with the  holding period requirements  of Rule 144.  Rule 701  further
provides  that  non-affiliates may  sell  such shares  in  reliance on  Rule 144
without having  to comply  with  the public  information, volume  limitation  or
notice  provisions of Rule  144. In both cases,  a holder of  Rule 701 shares is
required to wait until 90 days after the date of this Prospectus before  selling
such shares.
 
    The Company intends to file registration statements under the Securities Act
180  days after the Effective  Date to register shares  of Common Stock reserved
for issuance under the  Stock Plan and the  Directors Plan, thus permitting  the
resale of such shares by non-affiliates in the public market without restriction
under  the Securities Act. Such  registration statements will become immediately
upon filing.
 
    As of April  30, 1996, the  holders of approximately  15,834,537 shares  are
entitled  to certain registration rights with respect to such shares. If a large
number of such shares were registered and sold in the public market, such  sales
could have an adverse effect on the market price for the Company's Common Stock.
If  the Company were required to include in a Company-initiated registration the
shares held  by such  holders pursuant  to the  exercise of  their  registration
rights,  such sales may have an adverse effect on the Company's ability to raise
needed capital.  See "Description  of Capital  Stock --  Registration Rights  of
Certain Shareholders."
 
    Prior to this offering, there has been no public market for the Common Stock
of  the Company and  no predictions can be  made as to the  effect, if any, that
market sales of shares of Common Stock prevailing from time to time may have  on
the market price of the Common Stock. Nevertheless, sales of significant numbers
of  shares of  the Common Stock  in the  public market may  adversely affect the
market price of the Common Stock  offered hereby and could impair the  Company's
future ability to raise capital through an offering of its equity securities.
 
                                       62
<PAGE>
                                  UNDERWRITING
 
    The   Underwriters  named   below  acting   through  their  representatives,
Robertson, Stephens & Company  LLC, CS First  Boston Corporation and  Montgomery
Securities  (the "Representatives"), have severally agreed, subject to the terms
and conditions of the  Underwriting Agreement to purchase  from the Company  the
number  of  shares of  Common Stock  set forth  opposite their  respective names
below. The Underwriters are committed to purchase and pay for all of such shares
if any are purchased:
 
   
<TABLE>
<CAPTION>
                                                                                              NUMBER OF
                                        UNDERWRITER                                             SHARES
- --------------------------------------------------------------------------------------------  ----------
<S>                                                                                           <C>
Robertson, Stephens & Company LLC...........................................................
CS First Boston Corporation.................................................................
Montgomery Securities.......................................................................
 
                                                                                              ----------
    Total...................................................................................   6,000,000
                                                                                              ----------
                                                                                              ----------
</TABLE>
    
 
    The Company has been  advised by the  Representatives that the  Underwriters
propose  to offer the shares of Common Stock to the public at the initial public
offering price set forth  on the cover  page of this  Prospectus and to  certain
dealers at such price, less a concession of not more than $  per share, of which
$      may be reallowed to other dealers. After the initial public offering, the
public offering price, concession and reallowances to dealers may be reduced  by
the Representatives.
 
    The  Underwriters may offer  up to $3  million worth of  the Common Stock to
Alejandro C. Zaffaroni, a  founder and director of  the Company, at the  initial
public  offering  price set  forth on  the  cover page  of this  Prospectus. The
Underwriters would not  receive an  underwriting discount or  commission on  the
sale of any of these shares of Common Stock to Dr. Zaffaroni.
 
   
    The  Company has granted  to the Underwriters  an option, exercisable during
the 30-day  period after  the date  of this  Prospectus, to  purchase up  to  an
additional  900,000 shares of  Common Stock at  the same price  per share as the
Company receives for the 6,000,000 shares  that the Underwriters have agreed  to
purchase.  To the extent that the Underwriters exercise such option, each of the
Underwriters will  have a  firm commitment  to purchase  approximately the  same
percentage  of such additional shares that the  number of shares of Common Stock
to be purchased by it shown in the above table represents as a percentage of the
6,000,000 shares offered hereby.  If purchased, such  additional shares will  be
sold  by the  Underwriters on  the same  terms as  those on  which the 6,000,000
shares are being sold. The Company will be obligated, pursuant to the option, to
sell shares  to the  Underwriters to  the extent  the option  is exercised.  The
Underwriters  may exercise  such option  only to  cover over-allotments  made in
connection with the sale of shares of Common Stock offered hereby.
    
 
    The Underwriting  Agreement  contains  covenants of  indemnity  between  the
Underwriters  and  the  Company  against  certain  civil  liabilities, including
liabilities under the Securities Act of 1933, as amended, and liability  arising
from  breaches of representations  and warranties contained  in the Underwriting
Agreement.
 
    Each  officer,   director   and  certain   shareholders   together   holding
approximately   12,643,742  shares  of   Common  Stock  have   agreed  with  the
Representatives that, until 180 days from the Effective Date, subject to certain
limited exceptions, they will not, directly or indirectly, sell, offer  contract
to sell, pledge, grant any option to purchase or otherwise dispose of any shares
of  Common Stock or any securities convertible into, or exchangeable for, or any
rights to purchase or  acquire, shares of Common  Stock, owned directly by  such
holders or with respect to which they have the power of disposition, without the
prior  written  consent  of  Robertson, Stephens  &  Company  LLC. Approximately
10,411,408 of such shares will be  eligible for immediate public sale  following
expiration  of the  lock-up period pursuant  to Rule 144.  Robertson, Stephens &
Company LLC may, in its sole discretion and at any time without notice,  release
all or any portion of the securities subject to lock-up agreements. In addition,
the Company has agreed that, until 180 days from the Effective Date, the Company
will  not, without  the prior written  consent of Robertson,  Stephens & Company
LLC, subject to certain  limited exceptions, sell or  otherwise dispose of,  any
shares   of   Common   Stock,  any   options   or  warrants   to   purchase  any
 
                                       63
<PAGE>
shares of Common Stock  or any securities convertible  into, exercisable for  or
exchangeable  for shares of Common Stock other than the Company's sale of shares
in this  offering,  the  issuance of  Common  Stock  upon the  exercise  of  the
outstanding  warrants or options, or the Company's grant of options and issuance
of stock  under existing  employee stock  option or  stock purchase  plans.  See
"Shares Eligible for Future Sale."
 
    The  Underwriters do not intend to confirm sales to accounts over which they
exercise discretionary authority.
 
    Prior to this offering, there has been no public market for the Common Stock
of the Company. Consequently, the initial  public offering price for the  Common
Stock   was  determined  through  negotiations   between  the  Company  and  the
Representatives. The  material  factors  considered in  such  negotiations  were
prevailing  market conditions, certain  financial information of  the Company in
recent periods, market valuations  of other companies that  the Company and  the
Representatives  believed  to be  comparable to  the  Company, estimates  of the
business  potential  of  the  Company,  the  present  state  of  the   Company's
development and the Company's management.
 
    A   managing  director   of  CS  First   Boston  Corporation,   one  of  the
Representatives, is the beneficial owner of 7,407 shares of Common Stock.
 
                                 LEGAL MATTERS
 
    The validity of the Common Stock offered hereby will be passed upon for  the
Company  by Heller  Ehrman White &  McAuliffe, Palo Alto,  California. Julian N.
Stern, the  beneficial owner  of 26,980  shares  of Common  Stock, is  the  sole
shareholder  and employee  of a  professional corporation  that is  a partner of
Heller Ehrman White & McAuliffe. Certain legal matters relating to the  offering
will  be passed upon for the Underwriters by Wilson, Sonsini, Goodrich & Rosati,
Palo Alto, California.
 
                                    EXPERTS
 
    The financial statements of  Affymetrix at December 31,  1994 and 1995,  and
for  the  years  ended December  31,  1993,  1994 and  1995,  appearing  in this
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.
 
                             ADDITIONAL INFORMATION
 
    The  Company  has filed  with the  Securities  and Exchange  Commission (the
"Commission") a Registration Statement, of  which this Prospectus constitutes  a
part,  under  the Securities  Act with  respect  to the  shares of  Common Stock
offered hereby.  This  Prospectus omits  certain  information contained  in  the
Registration  Statement, and reference is made to the Registration Statement and
the exhibits and schedules thereto for  further information with respect to  the
Company  and  the  Common Stock  offered  hereby. Statements  contained  in this
Prospectus as to the provisions of  any referenced contracts or other  documents
summarize the material elements of such contracts or documents. Such statements,
however, are not necessarily complete, and in each instance reference is made to
the  copy of such  document filed as  an exhibit to  the Registration Statement.
Each such  statement  is  qualified  in its  entirety  by  such  reference.  The
Registration Statement, including exhibits and schedules filed therewith, may be
inspected  without charge at  the public reference  facilities maintained by the
Commission at Room 1024,  Judiciary Plaza, 450  Fifth Street, N.W.,  Washington,
D.C.  20549 and  at the regional  offices of  the Commission located  at 7 World
Trade Center, Suite 1300, New York, New York 10048 and Citicorp Center, 500 West
Madison Street, Suite 1400,  Chicago, Illinois 60661.  Copies of such  materials
may  be obtained from the Public Reference Section of the Commission, Room 1024,
Judiciary Plaza, 450 Fifth Street, N.W., Washington, D.C. 20549, and its  public
reference  facilities in New York, New York and Chicago, Illinois, at prescribed
rates.
 
                                       64
<PAGE>
                                    GLOSSARY
 
<TABLE>
<S>                                 <C>
Amplification.....................  An  increase in the number of  copies of specific DNA or
                                    RNA fragments.
Base..............................  The nucleotides that comprise DNA.
Chromosomes.......................  The  self-replicating   genetic  structures   in   cells
                                    containing the cellular DNA that bears in its nucleotide
                                     sequence the linear array of genes.
Complementary sequence............  Nucleic   acid   base   sequences   that   can   form  a
                                    double-stranded structure  by matching  base pairs;  the
                                     complementary sequence to GTAC is CATG.
DNA (deoxyribonucleic acid).......  The  molecule that encodes genetic information. DNA is a
                                    double-stranded molecule  held  together by  weak  bonds
                                     between base pairs. The four nucleotides in DNA contain
                                     the  bases adenine  (A), guanine (G),  cytosine (C) and
                                     thymine (T). In nature, base pairs form only between  A
                                     and  T and between G and  C; thus, the base sequence of
                                     each single  strand can  be deduced  from that  of  its
                                     complementary sequence.
DNA sequence......................  The  relative order of base pairs, whether in a fragment
                                    of DNA, a gene, a chromosome, or an entire genome.
DNA synthesis.....................  The process  of  building strands  of  nucleotide  bases
                                    through controlled chemical reactions.
Feature...........................  A  discrete section of a probe array containing millions
                                    of copies  of  the  same DNA  probe.  Each  probe  array
                                     contains  from 16,000  to more  than 100,000 individual
                                     features.
Fluorescent label.................  A compound that may be attached to another molecule  and
                                    that is capable of emitting light. The emitted light may
                                     be  detected to  determine the presence  or location of
                                     the molecule.
Gel-based sequencing..............  Determination  of   the  order   of  nucleotides   (base
                                    sequences)  in  a  DNA  molecule  using  a  matrix  of a
                                     polymeric molecule  to  form  a  gel,  which  separates
                                     pieces  of DNA  in an  electric field  based upon their
                                     sizes.
Gene..............................  The  fundamental   physical  and   functional  unit   of
                                    heredity.  A gene is an  ordered sequence of nucleotides
                                     located  in  a  particular  position  on  a  particular
                                     chromosome that encodes a specific functional product.
Gene expression...................  The  process by which a gene's coded information creates
                                    the  structures  present  and  operating  in  the  cell.
                                     Expressed genes include those that are transcribed into
                                     mRNA  and then  translated into protein  and those that
                                     are  transcribed  into  RNA  but  not  translated  into
                                     protein.
Gene expression monitoring........  The  process of correlating the level and timing of gene
                                    expression with abnormal cellular behavior and disease.
Genetic code......................  The sequence of nucleotides, coded in triplets along the
                                    mRNA, that  determines the  sequence of  amino acids  in
                                     protein  synthesis. The DNA  sequence of a  gene can be
                                     used to predict the mRNA sequence, and the genetic code
                                     can in turn be used to predict the amino acid sequence.
</TABLE>
 
                                       65
<PAGE>
<TABLE>
<S>                                 <C>
Genetic mapping...................  Determining the  relative positions  of genes  on a  DNA
                                    molecule and the distance between them.
Genetic marker....................  An identifiable physical location on a chromosome, whose
                                     inheritance can be monitored.
Genome............................  All  the  genetic  material  in  the  chromosomes  of  a
                                    particular organism. Genome size  is generally given  as
                                     its total number of base pairs.
Genomics..........................  The study of genes and their function.
High-throughput sequencing........  The   process  of   identifying  and   sequencing  small
                                    stretches of  genes expressed  in  a certain  cell  type
                                     using gel-based sequencing techniques.
HIV...............................  Human  Immunodeficiency Virus, the virus responsible for
                                    HIV  disease   and   its   end-stage,   AIDS   (Acquired
                                     Immunodeficiency Syndrome).
Human Genome Project..............  Collective  name for  several projects begun  in 1986 by
                                    United States Department of  Energy to map and  sequence
                                     the   human  genome  and  develop  new  techniques  and
                                     instruments for detecting and analyzing DNA.
Hybridization.....................  The process of joining two complementary strands of  DNA
                                    or  one each  of DNA and  RNA to  form a double-stranded
                                     molecule.
Immunoassay.......................  A diagnostic test  that uses a  protein produced by  the
                                    immune  system, called  an antibody,  to detect specific
                                     proteins that may be used to aid in the  identification
                                     or treatment of disease.
In vitro..........................  Studies  or phenomena  that take place  outside the body
                                    (for instance, in test tubes).
Linkage analysis..................  Locating of  genes  on chromosomes  by  determining  the
                                    inheritance  patterns of genetic  markers that are close
                                     to one another.
mRNA (messenger RNA)..............  RNA that serves as a template for protein synthesis. See
                                    "Genetic code."
Mutation..........................  A transmissible  change in  the genetic  material of  an
                                    organism, usually in a single gene.
Nucleic acid......................  A large molecule composed of nucleotide subunits.
Nucleotide........................  A subunit of DNA or RNA consisting of a nitrogenous base
                                     (adenine,   guanine,  thymine,  or   cytosine  in  DNA;
                                     adenine,  guanine,  uracil,  or  cytosine  in  RNA),  a
                                     phosphate molecule and a sugar molecule (deoxyribose in
                                     DNA,  ribose  in  RNA).  Thousands  of  nucleotides are
                                     linked to form a DNA or RNA molecule.
Nucleotide pair...................  Two nitrogenous bases  (adenine and  thymine or  guanine
                                    and  cytosine) held together by  weak bonds. Two strands
                                     of DNA are held together in the shape of a double helix
                                     by the bonds between base pairs.
Polymorphism......................  Difference in DNA sequence among individuals.
Polymorphism Screening............  The  process  of  correlating  genetic  variations  with
                                    disease or traits.
Photolithography..................  A technique that uses light to induce chemical reactions
                                    that create exposure patterns on a surface.
</TABLE>
 
                                       66
<PAGE>
<TABLE>
<S>                                 <C>
Probe.............................  Short  sequence of DNA used to identify longer stretches
                                    of complementary DNA or RNA sequence.
Probe array.......................  Small, disposable chip consisting of densely packed  DNA
                                     sequences  (probes), where the identity and position of
                                     each probe is known on the chip surface.
Protein...........................  A large molecule composed of one or more chains of amino
                                    acids in a  specific order; the  order is determined  by
                                     the  base sequence of nucleotides  in the gene or genes
                                     coding for the protein.  Proteins are required for  the
                                     structure, function and regulation of the body's cells,
                                     tissues,  and  organs,  and  each  protein  has  unique
                                     functions. Examples of proteins are hormones,  enzymes,
                                     and antibodies.
RNA (Ribonucleic acid)............  A  chemical found in the nucleus and cytoplasm of cells;
                                    it plays  an important  role  in protein  synthesis  and
                                     other chemical activities of the cell. The structure of
                                     RNA  is  similar  to  that of  DNA.  There  are several
                                     classes of  RNA  molecules,  including  messenger  RNA,
                                     transfer RNA, ribosomal RNA, and other small RNAs, each
                                     serving a different purpose.
Solid-phase DNA synthesis.........  DNA  synthesis in which the chains of bases are anchored
                                    to a solid substrate, such as glass, as opposed to being
                                     synthesized in solution.
Virus.............................  A noncellular biological entity that can reproduce  only
                                    within  a  host cell.  Viruses  consist of  nucleic acid
                                     covered  by  protein.  Some  animal  viruses  are  also
                                     surrounded  by membrane. Once inside the infected cell,
                                     the virus uses the synthetic capability of the host  to
                                     produce progeny virus.
Wafer.............................  Pieces  of  glass  on which  multiple  probe  arrays are
                                    simultaneously manufactured. The wafers are subsequently
                                     diced to yield individual probe arrays.
</TABLE>
 
                                       67
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                         INDEX TO FINANCIAL STATEMENTS
 
<TABLE>
<CAPTION>
                                                                                                                PAGE
                                                                                                                -----
<S>                                                                                                          <C>
Report of Ernst & Young LLP, Independent Auditors..........................................................         F-2
 
Financial Statements:
  Balance Sheets...........................................................................................         F-3
  Statements of Operations.................................................................................         F-4
  Statement of Shareholders' Equity........................................................................         F-5
  Statements of Cash Flows.................................................................................         F-7
  Notes to Financial Statements............................................................................         F-8
</TABLE>
 
                                      F-1
<PAGE>
               REPORT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS
 
The Board of Directors and Shareholders
Affymetrix, Inc.
 
    We  have  audited the  accompanying balance  sheets  of Affymetrix,  Inc. (a
development stage  company) at  December  31, 1994  and  1995, and  the  related
statements  of operations, shareholders' equity, and  cash flows for each of the
three years  in the  period ended  December 31,  1995 and  for the  period  from
inception (January 1, 1991) to December 31, 1995. 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.  (a
development stage company) at December 31, 1994 and 1995, and the results of its
operations  and its cash flows  for each of the three  years in the period ended
December 31,  1995  and for  the  period from  inception  (January 1,  1991)  to
December 31, 1995, in conformity with generally accepted accounting principles.
 
   
                                          /s/ ERNST & YOUNG LLP
    
   
Palo Alto, California
February 9, 1996,
except for the first paragraph of Note 9 as to which the date is
May 20, 1996
    
 
                                      F-2
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                                 BALANCE SHEETS
                      (IN THOUSANDS, EXCEPT SHARE AMOUNTS)
 
                                     ASSETS
 
<TABLE>
<CAPTION>
                                                                     DECEMBER 31,
                                                                 --------------------
                                                                   1994       1995
                                                                 ---------  ---------   MARCH 31,     PRO FORMA
                                                                                       -----------  SHAREHOLDERS'
                                                                                          1996        EQUITY AT
                                                                                       -----------    MARCH 31,
                                                                                                    -------------
                                                                                       (UNAUDITED)      1996
                                                                                                    -------------
                                                                                                     (UNAUDITED)
<S>                                                              <C>        <C>        <C>          <C>
Current assets:
  Cash and cash equivalents....................................  $   6,659  $   2,481   $     308
  Short-term investments.......................................     11,146     36,402      34,529
  Contract and grant receivables...............................         90      1,342         636
  Inventories..................................................     --            670       1,469
  Other current assets.........................................         88        260         422
                                                                 ---------  ---------  -----------
    Total current assets.......................................     17,983     41,155      37,364
Property and equipment, at cost:
  Equipment and furniture......................................      2,554      4,254       4,955
  Leasehold improvements.......................................        356        586         587
                                                                 ---------  ---------  -----------
                                                                     2,910      4,840       5,542
  Less accumulated depreciation and amortization...............     (1,047)    (1,583)     (1,863)
                                                                 ---------  ---------  -----------
    Net property and equipment.................................      1,863      3,257       3,679
Other assets...................................................         15        140         142
                                                                 ---------  ---------  -----------
                                                                 $  19,861  $  44,552   $  41,185
                                                                 ---------  ---------  -----------
                                                                 ---------  ---------  -----------
                               LIABILITIES AND SHAREHOLDERS' EQUITY
Current liabilities:
  Accounts payable and other accrued liabilities...............  $   1,046  $   2,469   $   3,278
  Payable to Affymax...........................................        254         89          12
  Deferred revenue.............................................        837      2,340       2,153
  Current portion of capital lease obligation..................        169        187         192
                                                                 ---------  ---------  -----------
    Total current liabilities..................................      2,306      5,085       5,635
Convertible note payable to Affymax............................      6,000     --          --
Noncurrent portion of capital lease obligation.................      1,135        948         898
Advance from collaborative partner.............................      1,250     --          --
Commitments....................................................                            --
Shareholders' equity:
  Convertible preferred stock, no par value; 27,500,000 shares
   authorized; 14,500,000 issued and outstanding at December
   31, 1994, 23,166,666 at December 31, 1995 and March 31, 1996
   (none pro forma); aggregate liquidation preference of
   $70,625 at December 31, 1995 and March 31, 1996.............     31,283     70,439      70,439     $  --
  Common stock, no par value; 50,000,000 shares authorized;
   408,198 shares issued and outstanding at December 31, 1994,
   536,267 at December 31, 1995 and 609,240 at March 31, 1996
   (16,239,231 pro forma)......................................        122      2,717       3,089        73,528
  Notes receivable from officers...............................        (84)       (42)        (41)          (41)
  Unrealized gain(loss) on available-for-sale securities.......       (382)       281           1             1
  Deferred compensation........................................     --         (2,360)     (2,399)       (2,399)
  Deficit accumulated during development stage.................    (21,769)   (32,516)    (36,437)      (36,437)
                                                                 ---------  ---------  -----------  -------------
    Total shareholders' equity.................................      9,170     38,519      34,652     $  34,652
                                                                 ---------  ---------  -----------  -------------
                                                                                                    -------------
                                                                 $  19,861  $  44,552   $  41,185
                                                                 ---------  ---------  -----------
                                                                 ---------  ---------  -----------
</TABLE>
 
                            See accompanying notes.
 
                                      F-3
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                            STATEMENTS OF OPERATIONS
                    (IN THOUSANDS, EXCEPT PER SHARE AMOUNT)
 
<TABLE>
<CAPTION>
                                          YEAR ENDED DECEMBER 31,
                                      -------------------------------
                                        1993       1994       1995
                                      ---------  ---------  ---------        THREE MONTHS          PERIOD FROM
                                                                           ENDED MARCH 31,          INCEPTION
                                                                       ------------------------    (JANUARY 1,
                                                                          1995         1996           1991)
                                                                       -----------  -----------      THROUGH
                                                                                                 MARCH 31, 1996
                                                                       (UNAUDITED)  (UNAUDITED)  ---------------
                                                                                                   (UNAUDITED)
<S>                                   <C>        <C>        <C>        <C>          <C>          <C>
Contract and grant revenue..........  $   1,413  $   1,574  $   4,625   $     854    $   1,416      $   9,071
Operating expenses:
  Research and development..........      6,566      9,483     12,420       2,274        4,177         38,328
  General and administrative........        577      2,303      3,833         777        1,649          9,205
                                      ---------  ---------  ---------  -----------  -----------       -------
    Total operating expenses
     (includes related-party expense
     of $1,147, $1,647, $1,432,
     $428, $364 and $4,590,
     respectively)..................      7,143     11,786     16,253       3,051        5,826         47,533
                                      ---------  ---------  ---------  -----------  -----------       -------
Loss from operations................     (5,730)   (10,212)   (11,628)     (2,197)      (4,410)       (38,462)
  Interest income...................        211        575      1,301         183          517          2,607
  Interest expense (includes
   related-party expense of $320 in
   1995 and $128 in the three months
   ended March 31, 1995)............        (73)       (43)      (420)       (160)         (28)          (582)
                                      ---------  ---------  ---------  -----------  -----------       -------
Net loss............................  $  (5,592) $  (9,680) $ (10,747)  $  (2,174)   $  (3,921)     $ (36,437)
                                      ---------  ---------  ---------  -----------  -----------       -------
                                      ---------  ---------  ---------  -----------  -----------       -------
Pro forma net loss per share........                        $   (0.61)  $   (0.12)   $   (0.22)
                                                            ---------  -----------  -----------
                                                            ---------  -----------  -----------
Shares used in computing pro forma
 net loss per share.................                           17,664      17,663       17,664
                                                            ---------  -----------  -----------
                                                            ---------  -----------  -----------
</TABLE>
 
                            See accompanying notes.
 
                                      F-4
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                       STATEMENT OF SHAREHOLDERS' EQUITY
       FOR THE PERIOD FROM INCEPTION (JANUARY 1, 1991) TO MARCH 31, 1996
               (IN THOUSANDS, EXCEPT SHARE AND PER SHARE AMOUNTS)
<TABLE>
<CAPTION>
                                                                                  CONTRI-
                                        CONVERTIBLE                   NOTES       BUTIONS
                                         PREFERRED     COMMON      RECEIVABLE      FROM      UNREALIZED       DEFERRED
                                           STOCK        STOCK     FROM OFFICERS   AFFYMAX    GAIN (LOSS)    COMPENSATION
                                        -----------  -----------  -------------  ---------  -------------  ---------------
<S>                                     <C>          <C>          <C>            <C>        <C>            <C>
Issuance of 666 shares of common stock
 for cash in March 1992 at $0.15 per
 share................................   $  --        $  --         $  --        $  --        $  --           $  --
Contributions from Affymax (1991 and
 1992)................................      --           --            --            6,316       --              --
Net loss (1991 and 1992)..............      --           --            --           --           --              --
                                        -----------  -----------          ---    ---------        -----          ------
Balance at December 31, 1992..........      --           --            --            6,316       --              --
Contributions from Affymax through
 September 1993.......................      --           --            --            4,309       --              --
Issuance of 6,000,000 shares of Series
 A Senior convertible preferred stock
 for cash in September 1993, at $3.50
 per share, net of issuance costs of
 $342.................................      20,658       --            --           --           --              --
Conversion of all contributions from
 Affymax into 8,500,000 shares of
 Series 1 Subordinated convertible
 preferred stock in September 1993 at
 $1.25 per share......................      10,625       --            --          (10,625)      --              --
Issuance of 66,666 shares of common
 stock for cash upon exercise of stock
 options in December 1993 at $0.30 per
 share................................      --               20        --           --           --              --
Issuance of 266,666 shares of common
 stock for notes receivable upon
 exercise of options in December 1993
 at $0.30 per share...................      --               80           (80)      --           --              --
Net loss..............................      --           --            --           --           --              --
                                        -----------  -----------          ---    ---------        -----          ------
Balance at December 31, 1993..........      31,283          100           (80)      --           --              --
Issuance of 74,200 shares of common
 stock for cash upon exercise of stock
 options at $0.30 per share...........      --               22        --           --           --              --
Interest accrued on notes receivable
 from officers........................      --           --                (4)      --           --              --
Unrealized loss on available-for-sale
 securities...........................      --           --            --           --             (382)         --
Net loss..............................      --           --            --           --           --              --
                                        -----------  -----------          ---    ---------        -----          ------
Balance at December 31, 1994..........      31,283          122           (84)      --             (382)         --
Issuance of 7,333,333 shares of Series
 B Senior convertible preferred stock
 for cash in August 1995, at $4.50 per
 share, net of issuance costs of
 $164.................................      32,836       --            --           --           --              --
Conversion of $6,000 note payable into
 1,333,333 shares of Series B Senior
 convertible preferred stock in August
 1995, at $4.50 per share.............       6,000       --            --           --           --              --
Issuance of 62,749 shares of common
 stock for cash upon exercise of stock
 options at $0.30 to $0.675 per
 share................................      --               23        --           --           --              --
Issuance of 65,320 shares of common
 stock for financing commissions in
 August 1995 at $0.675 per share......      --               44        --           --           --              --
 
<CAPTION>
                                           DEFICIT         TOTAL
                                         ACCUMULATED   SHAREHOLDERS'
                                           DURING       EQUITY (NET
                                         DEVELOPMENT      CAPITAL
                                            STAGE       DEFICIENCY)
                                        -------------  -------------
<S>                                     <C>            <C>
Issuance of 666 shares of common stock
 for cash in March 1992 at $0.15 per
 share................................    $  --          $  --
Contributions from Affymax (1991 and
 1992)................................       --              6,316
Net loss (1991 and 1992)..............       (6,497)        (6,497)
                                        -------------  -------------
Balance at December 31, 1992..........       (6,497)          (181)
Contributions from Affymax through
 September 1993.......................       --              4,309
Issuance of 6,000,000 shares of Series
 A Senior convertible preferred stock
 for cash in September 1993, at $3.50
 per share, net of issuance costs of
 $342.................................       --             20,658
Conversion of all contributions from
 Affymax into 8,500,000 shares of
 Series 1 Subordinated convertible
 preferred stock in September 1993 at
 $1.25 per share......................       --             --
Issuance of 66,666 shares of common
 stock for cash upon exercise of stock
 options in December 1993 at $0.30 per
 share................................       --                 20
Issuance of 266,666 shares of common
 stock for notes receivable upon
 exercise of options in December 1993
 at $0.30 per share...................       --             --
Net loss..............................       (5,592)        (5,592)
                                        -------------  -------------
Balance at December 31, 1993..........      (12,089)        19,214
Issuance of 74,200 shares of common
 stock for cash upon exercise of stock
 options at $0.30 per share...........       --                 22
Interest accrued on notes receivable
 from officers........................       --                 (4)
Unrealized loss on available-for-sale
 securities...........................       --               (382)
Net loss..............................       (9,680)        (9,680)
                                        -------------  -------------
Balance at December 31, 1994..........      (21,769)         9,170
Issuance of 7,333,333 shares of Series
 B Senior convertible preferred stock
 for cash in August 1995, at $4.50 per
 share, net of issuance costs of
 $164.................................       --             32,836
Conversion of $6,000 note payable into
 1,333,333 shares of Series B Senior
 convertible preferred stock in August
 1995, at $4.50 per share.............       --              6,000
Issuance of 62,749 shares of common
 stock for cash upon exercise of stock
 options at $0.30 to $0.675 per
 share................................       --                 23
Issuance of 65,320 shares of common
 stock for financing commissions in
 August 1995 at $0.675 per share......       --                 44
</TABLE>
 
                                      F-5
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                 STATEMENT OF SHAREHOLDERS' EQUITY (CONTINUED)
       FOR THE PERIOD FROM INCEPTION (JANUARY 1, 1991) TO MARCH 31, 1996
               (IN THOUSANDS, EXCEPT SHARE AND PER SHARE AMOUNTS)
<TABLE>
<CAPTION>
                                                                                  CONTRI-
                                        CONVERTIBLE                   NOTES       BUTIONS
                                         PREFERRED     COMMON      RECEIVABLE      FROM      UNREALIZED       DEFERRED
                                           STOCK        STOCK     FROM OFFICERS   AFFYMAX    GAIN (LOSS)    COMPENSATION
                                        -----------  -----------  -------------  ---------  -------------  ---------------
<S>                                     <C>          <C>          <C>            <C>        <C>            <C>
Issuance of warrants in June, July,
 and October 1995 for 202,441 of
 Series 2 Subordinated convertible
 preferred stock at $1.58 per share in
 exchange for interest................         320       --            --           --           --              --
Interest received on notes receivable
 from officers........................      --           --                 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 at December 31, 1995..........      70,439        2,717           (42)      --              281          (2,360)
Issuance of 72,973 shares of common
 stock for cash upon exercise of stock
 options at $0.30 to $0.675 per share
 (Unaudited)..........................      --               46        --           --           --              --
Interest received on notes receivable
 from officers (Unaudited)............      --           --                 1       --           --              --
Deferred compensation related to grant
 of stock options (Unaudited).........      --              326        --           --           --                (326)
Amortization of deferred compensation
 (Unaudited)..........................      --           --            --           --           --                 287
Unrealized loss on available-for-sale
 securities (Unaudited)...............      --           --            --           --             (280)         --
Net loss (Unaudited)..................      --           --            --           --           --              --
                                        -----------  -----------          ---    ---------        -----          ------
Balance at March 31, 1996
 (Unaudited)..........................   $  70,439    $   3,089     $     (41)   $  --        $       1       $  (2,399)
                                        -----------  -----------          ---    ---------        -----          ------
                                        -----------  -----------          ---    ---------        -----          ------
 
<CAPTION>
                                           DEFICIT         TOTAL
                                         ACCUMULATED   SHAREHOLDERS'
                                           DURING       EQUITY (NET
                                         DEVELOPMENT      CAPITAL
                                            STAGE       DEFICIENCY)
                                        -------------  -------------
<S>                                     <C>            <C>
Issuance of warrants in June, July,
 and October 1995 for 202,441 of
 Series 2 Subordinated convertible
 preferred stock at $1.58 per share in
 exchange for interest................       --                320
Interest received on notes receivable
 from officers........................       --                  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 at December 31, 1995..........      (32,516)        38,519
Issuance of 72,973 shares of common
 stock for cash upon exercise of stock
 options at $0.30 to $0.675 per share
 (Unaudited)..........................       --                 46
Interest received on notes receivable
 from officers (Unaudited)............       --                  1
Deferred compensation related to grant
 of stock options (Unaudited).........       --             --
Amortization of deferred compensation
 (Unaudited)..........................       --                287
Unrealized loss on available-for-sale
 securities (Unaudited)...............       --               (280)
Net loss (Unaudited)..................       (3,921)        (3,921)
                                        -------------  -------------
Balance at March 31, 1996
 (Unaudited)..........................    $ (36,437)     $  34,652
                                        -------------  -------------
                                        -------------  -------------
</TABLE>
 
                             See accompanyng notes.
 
                                      F-6
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                            STATEMENTS OF CASH FLOWS
                INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS
                                 (IN THOUSANDS)
<TABLE>
<CAPTION>
                                                                     YEAR ENDED DECEMBER 31,      THREE MONTHS ENDED MARCH
                                                                 -------------------------------            31,
                                                                   1993       1994       1995     ------------------------
                                                                 ---------  ---------  ---------     1995         1996
                                                                                                  -----------  -----------
                                                                                                  (UNAUDITED)  (UNAUDITED)
<S>                                                              <C>        <C>        <C>        <C>          <C>
Cash flows from operating activities:
  Net loss.....................................................  $  (5,592) $  (9,680) $ (10,747)  $  (2,174)   $  (3,921)
Adjustments to reconcile net loss to net cash used in operating
 activities:
    Depreciation and amortization..............................        465        689        701         150          279
    Amortization of investment premiums and discounts, net.....     --            148       (191)        165          (24)
    Loss on disposal of equipment..............................     --            417        188      --           --
    Compensation due to accelerated vesting....................     --         --             40      --           --
    Amortization of deferred compensation......................     --         --            128      --              287
    Interest payable exchanged for warrants....................     --         --            320      --           --
    Changes in operating assets and liabilities:
      Contract and grant receivables...........................     --            (90)    (1,252)       (675)         706
      Inventories..............................................     --         --           (670)     --             (799)
      Other current assets.....................................       (649)       575       (172)        (19)        (162)
      Other assets.............................................         14        (15)       (80)     --               (2)
      Accounts payable and other accrued liabilities...........        570        295      1,423        (196)         809
      Payable to Affymax.......................................      1,574     (1,320)      (165)         (1)         (77)
      Deferred revenue.........................................        460        377        253        (150)        (187)
      Advance from collaborative partner.......................     --          1,250     --          --           --
                                                                 ---------  ---------  ---------  -----------  -----------
        Net cash used in operating activities..................     (3,158)    (7,354)   (10,224)     (2,900)      (3,091)
                                                                 ---------  ---------  ---------  -----------  -----------
Cash flows from investing activities:
    Capital expenditures.......................................     (1,537)    (1,207)    (2,283)       (580)        (701)
    Proceeds from the sale of available-for-sale securities....     --          5,308      8,538      --            1,466
    Proceeds from maturities of available-for-sale
     securities................................................     --         --          5,485      --            2,156
    Purchases of available-for-sale securities.................    (13,997)    (2,990)   (38,428)     (2,007)      (2,004)
                                                                 ---------  ---------  ---------  -----------  -----------
        Net cash provided by/(used in) investing activities....    (15,534)     1,111    (26,688)     (2,587)         917
                                                                 ---------  ---------  ---------  -----------  -----------
Cash flows from financing activities:
  Contributions from Affymax...................................      4,309     --         --          --           --
  Issuances of common stock....................................         20         22         23      --               46
  Issuances of preferred stock, net............................     20,658     --         32,880      --           --
  Proceeds from capital lease obligation.......................     --          1,307     --          --           --
  Principal payments on capital lease obligation...............     --             (3)      (169)        (41)         (45)
  Issuance of convertible note payable to Affymax..............     --          6,000     --          --           --
  Issuance of notes payable....................................        333     --         --          --           --
  Principal payments on notes payable..........................       (327)      (819)    --          --           --
                                                                 ---------  ---------  ---------  -----------  -----------
        Net cash provided by (used in) financing activities....     24,993      6,507     32,734         (41)           1
                                                                 ---------  ---------  ---------  -----------  -----------
Net increase (decrease) in cash and cash equivalents...........      6,301        264     (4,178)     (5,528)      (2,173)
Cash and cash equivalents at beginning of period...............         94      6,395      6,659       6,659        2,481
                                                                 ---------  ---------  ---------  -----------  -----------
Cash and cash equivalents at end of period.....................  $   6,395  $   6,659  $   2,481   $   1,131    $     308
                                                                 ---------  ---------  ---------  -----------  -----------
                                                                 ---------  ---------  ---------  -----------  -----------
Supplemental disclosure of noncash financing activities:
  Issuance of common stock for note receivable from officers...  $      80  $  --      $  --       $  --        $  --
                                                                 ---------  ---------  ---------  -----------  -----------
                                                                 ---------  ---------  ---------  -----------  -----------
  Conversion of note payable and contributions from
   Affymax to preferred stock..................................  $  10,625  $  --      $   6,000   $  --        $  --
                                                                 ---------  ---------  ---------  -----------  -----------
                                                                 ---------  ---------  ---------  -----------  -----------
  Assets under capital lease obligation........................     --      $   1,297  $  --       $  --        $  --
                                                                 ---------  ---------  ---------  -----------  -----------
                                                                 ---------  ---------  ---------  -----------  -----------
  Issuance of common stock for financing commissions...........  $  --      $  --      $      44   $  --        $  --
                                                                 ---------  ---------  ---------  -----------  -----------
                                                                 ---------  ---------  ---------  -----------  -----------
  Issuance of warrants in exchange for interest payable........  $  --      $  --      $     320   $  --        $  --
                                                                 ---------  ---------  ---------  -----------  -----------
                                                                 ---------  ---------  ---------  -----------  -----------
Supplemental disclosure of cash flow information:
  Interest paid................................................  $      73  $      20  $     122   $      32    $      28
                                                                 ---------  ---------  ---------  -----------  -----------
                                                                 ---------  ---------  ---------  -----------  -----------
 
<CAPTION>
                                                                  PERIOD FROM
                                                                  (JANUARY 1,
                                                                     1991)
                                                                 THROUGH MARCH
                                                                    31, 1996
 
<S>                                                              <C>
Cash flows from operating activities:
  Net loss.....................................................    $  (36,437)
Adjustments to reconcile net loss to net cash used in operating
 activities:
    Depreciation and amortization..............................         2,210
    Amortization of investment premiums and discounts, net.....           (67)
    Loss on disposal of equipment..............................           605
    Compensation due to accelerated vesting....................            40
    Amortization of deferred compensation......................           415
    Interest payable exchanged for warrants....................           320
    Changes in operating assets and liabilities:
      Contract and grant receivables...........................          (636)
      Inventories..............................................        (1,469)
      Other current assets.....................................          (422)
      Other assets.............................................           (98)
      Accounts payable and other accrued liabilities...........         3,278
      Payable to Affymax.......................................            12
      Deferred revenue.........................................           903
      Advance from collaborative partner.......................         1,250
                                                                 --------------
        Net cash used in operating activities..................       (30,096)
                                                                 --------------
Cash flows from investing activities:
    Capital expenditures.......................................        (6,494)
    Proceeds from the sale of available-for-sale securities....        15,312
    Proceeds from maturities of available-for-sale
     securities................................................         7,641
    Purchases of available-for-sale securities.................       (57,419)
                                                                 --------------
        Net cash provided by/(used in) investing activities....       (40,960)
                                                                 --------------
Cash flows from financing activities:
  Contributions from Affymax...................................        10,625
  Issuances of common stock....................................           111
  Issuances of preferred stock, net............................        53,538
  Proceeds from capital lease obligation.......................         1,307
  Principal payments on capital lease obligation...............          (217)
  Issuance of convertible note payable to Affymax..............         6,000
  Issuance of notes payable....................................         1,146
  Principal payments on notes payable..........................        (1,146)
                                                                 --------------
        Net cash provided by (used in) financing activities....        71,364
                                                                 --------------
Net increase (decrease) in cash and cash equivalents...........           308
Cash and cash equivalents at beginning of period...............        --
                                                                 --------------
Cash and cash equivalents at end of period.....................    $      308
                                                                 --------------
                                                                 --------------
Supplemental disclosure of noncash financing activities:
  Issuance of common stock for note receivable from officers...    $       80
                                                                 --------------
                                                                 --------------
  Conversion of note payable and contributions from
   Affymax to preferred stock..................................    $   16,625
                                                                 --------------
                                                                 --------------
  Assets under capital lease obligation........................    $    1,297
                                                                 --------------
                                                                 --------------
  Issuance of common stock for financing commissions...........    $       44
                                                                 --------------
                                                                 --------------
  Issuance of warrants in exchange for interest payable........    $      320
                                                                 --------------
                                                                 --------------
Supplemental disclosure of cash flow information:
  Interest paid................................................    $      262
                                                                 --------------
                                                                 --------------
</TABLE>
 
                            See accompanying notes.
 
                                      F-7
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                         NOTES TO FINANCIAL STATEMENTS
 
                    (INFORMATION FOR THE THREE MONTHS ENDED
                   MARCH 31, 1995 AND 1996 AND FOR THE PERIOD
                 FROM INCEPTION TO MARCH 31, 1996 IS UNAUDITED)
 
NOTE 1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
 
ORGANIZATION, OWNERSHIP, AND BUSINESS
 
    Affymetrix,  Inc. ("Affymetrix") is  a development stage  company focused on
developing  GeneChip-TM-  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.  Affymax
owns  approximately 46% of Affymetrix at December 31, 1995. In March 1995, Glaxo
plc, now Glaxo Wellcome plc ("Glaxo"), purchased Affymax, including its then 65%
interest in  Affymetrix.  The  accompanying  financial  statements  include  the
operations  of Affymetrix  from inception (January  1, 1991).  The advances from
Affymax through  September  1993  were recorded  as  capital  contributions  and
converted  to convertible  preferred shares  in September  1993. Since September
1993, the  financial  statements  reflect  the operations  of  Affymetrix  on  a
stand-alone basis.
 
    Affymetrix'  success  will  depend in  part  on  its ability  to  obtain and
maintain patent protection  in the  United States  and other  countries for  its
technologies  and products. The commercial success of Affymetrix also depends in
part on neither infringing  patents or proprietary rights  of third parties  nor
breaching any licenses that may relate to Affymetrix' technologies and products.
 
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.
 
INTERIM FINANCIAL INFORMATION
 
    The financial information at March 31, 1996 and for the three-month  periods
ended  March  31,  1995  and  1996 is  unaudited  but  includes  all adjustments
(consisting only  of normal  recurring adjustments)  which Affymetrix  considers
necessary for a fair presentation of the financial position at such date and the
operating  results and cash flows  for those periods. Results  for the March 31,
1996 period are not necessarily indicative of the results for the entire year.
 
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 earned. Direct  costs associated with  these
contracts  and grants are reported as  research and development expense. Revenue
for the  beta  shipments  are  recorded as  contract  revenue  pursuant  to  the
development agreements.
 
    Revenue  from customers representing 10% or more of total contract and grant
revenue during fiscal 1993, 1994, and 1995 is as follows:
 
<TABLE>
<CAPTION>
                1993        1994        1995
             ----------  ----------  ----------
<S>          <C>         <C>         <C>
 Customer:
     A           --          --             25%
     B           --          --             23%
     C           --          --             22%
     D              49%         54%         17%
     E              38%         29%      --
</TABLE>
 
                                      F-8
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                    (INFORMATION FOR THE THREE MONTHS ENDED
                   MARCH 31, 1995 AND 1996 AND FOR THE PERIOD
                 FROM INCEPTION TO MARCH 31, 1996 IS UNAUDITED)
 
NOTE 1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
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 initial filing of the proposed 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).
 
    Historical net loss per share information is as follows:
 
<TABLE>
<CAPTION>
                                                                           THREE MONTHS
                                                                              ENDED
                                  YEAR ENDED DECEMBER 31,                   MARCH 31,
                          ----------------------------------------  --------------------------
                              1993          1994          1995          1995          1996
                          ------------  ------------  ------------  ------------  ------------
<S>                       <C>           <C>           <C>           <C>           <C>
Net loss per share......  $      (0.75) $      (1.24) $      (1.38) $      (0.28) $      (0.50)
                          ------------  ------------  ------------  ------------  ------------
                          ------------  ------------  ------------  ------------  ------------
Shares used in computing
 net loss per share.....     7,422,000     7,801,000     7,812,000     7,811,000     7,812,000
                          ------------  ------------  ------------  ------------  ------------
                          ------------  ------------  ------------  ------------  ------------
</TABLE>
 
    Pro  forma net loss per share has  been computed as described above and also
gives effect  to the  conversion of  convertible preferred  shares not  included
above  that will  automatically convert  upon completion  of Affymetrix' initial
public offering  (using  the if-converted  method)  from the  original  date  of
issuance.
 
CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS
 
    Effective  January  1,  1994,  Affymetrix  adopted  Statement  of  Financial
Accounting Standards No. 115,  "Accounting for Certain  Investments in Debt  and
Equity  Securities." The effect of adopting Statement 115 at January 1, 1994 was
immaterial.
 
    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 December  31, 1995,  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.
 
                                      F-9
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                    (INFORMATION FOR THE THREE MONTHS ENDED
                   MARCH 31, 1995 AND 1996 AND FOR THE PERIOD
                 FROM INCEPTION TO MARCH 31, 1996 IS UNAUDITED)
 
NOTE 1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
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 $256,000 of raw material and $1,213,000 of finished goods at March
31, 1996.
 
DEPRECIATION AND AMORTIZATION
 
    The  costs of property and equipment 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.
Expenditures for maintenance and repairs are expensed as incurred.
 
ACCOUNTS PAYABLE AND OTHER ACCRUED LIABILITIES
 
    Accounts payable and  other accrued  liabilities include  the following  (in
thousands):
 
<TABLE>
<CAPTION>
                                                               DECEMBER 31,       MARCH 31,
                                                           --------------------  -----------
                                                             1994       1995        1996
                                                           ---------  ---------  -----------
<S>                                                        <C>        <C>        <C>
Accounts payable.........................................  $     587  $   1,088   $     963
Accrued compensation.....................................        262        576         617
Collaborative research refund............................     --            360         448
Accrued research.........................................        132        115         533
Legal....................................................     --            222         351
Other....................................................         65        108         366
                                                           ---------  ---------  -----------
                                                           $   1,046  $   2,469   $   3,278
                                                           ---------  ---------  -----------
                                                           ---------  ---------  -----------
</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
intends  to adopt the  disclosure only alternative under  Statement No. 123 and,
accordingly, Affymetrix will be required to disclose the pro forma net income or
loss and per share amounts  in the notes to  the financial statements using  the
fair  value based method. Affymetrix has not  yet determined the impact of these
pro forma adjustments.
 
CONCENTRATIONS OF CREDIT RISK
 
    Cash equivalents and investments are financial instruments which potentially
subject Affymetrix to  concentrations of  risk. 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 2.  COLLABORATIVE AGREEMENTS AND GRANTS
    Affymetrix expects  to collaborate  with  various partners  to  successfully
commercialize  its  technology. Total  costs incurred  under contract  and grant
arrangements  are  approximately  $1,412,000   in  1993,  $1,499,000  in   1994,
$5,237,000  in  1995,  $602,000  for  the three  months  ended  March  31, 1995,
$1,759,000 for the  three months  ended March 31,  1996 and  $9,952,000 for  the
period from inception through March 31, 1996.
 
                                      F-10
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                    (INFORMATION FOR THE THREE MONTHS ENDED
                   MARCH 31, 1995 AND 1996 AND FOR THE PERIOD
                 FROM INCEPTION TO MARCH 31, 1996 IS UNAUDITED)
 
NOTE 2.  COLLABORATIVE AGREEMENTS AND GRANTS (CONTINUED)
    Affymetrix  began  its  collaboration  with  Genetics  Institute  ("GI")  in
November  1994  to  develop   applications  of  the   GeneChip  system  to   the
identification  of new genes and new  uses of genes using expression monitoring.
Under  this  agreement,  GI  funded   Affymetrix'  research  to  determine   the
feasibility  of  this  application of  GeneChip  technology and  agreed  to make
milestone and royalty payments. Under certain circumstances, Affymetrix may  pay
royalty  payments to GI.  If Affymetrix enters into  similar agreements for gene
expression with third parties, Affymetrix may be required to refund a portion of
the  development  funding   received  from   GI  and  future   funding  may   be
proportionately reduced (see Note 9).
 
    In  December 1995, Affymetrix and GI expanded their relationship by entering
into a supply  agreement in the  field of genomics  under which Affymetrix  will
manufacture  and supply additional  custom probe arrays  based on specific genes
identified and selected by GI. Unlike the 1994 agreement with GI, this agreement
does not provide research funding to  Affymetrix. Pursuant to the agreement,  GI
is  obligated to purchase and Affymetrix  is obligated to supply certain minimum
quantities of custom probe arrays  developed for GI until  the later of 2001  or
four  years after development of specified probe arrays. Affymetrix will receive
fees for the design  and delivery of  the custom probe  arrays, and may  receive
milestone  payments and  royalties on therapeutic  compounds if  developed by GI
using these  probe arrays.  GI has  exclusive rights  to specific  probe  arrays
supplied by Affymetrix.
 
    In  October  1995,  Affymetrix  entered into  a  collaborative  research and
development agreement with Roche Molecular  Systems, Inc. ("Roche"). Under  this
agreement,  Roche agreed to fund certain  research efforts for approximately one
year aimed  at developing  GeneChip based  products designed  to detect  certain
genetic  mutations. Roche  is required  to make  additional payments  if certain
milestones  are  reached.  Under  certain  circumstances,  Affymetrix  may   pay
royalties to Roche.
 
    In  August 1995,  Affymetrix received a  three-year grant  from the National
Institutes of  Health ("NIH")  National  Center for  Human Genome  Research  for
approximately  $6,000,000. Affymetrix has  been awarded approximately $2,000,000
for the first year of the grant, and the remaining amounts are subject to yearly
appropriations by the NIH.
 
    Affymetrix entered into a collaboration with Hewlett-Packard Company  ("HP")
in  November 1994 for HP  to manufacture and supply  a more advanced scanner for
the use with Affymetrix'  GeneChip probe arrays and  for Affymetrix to  develop,
manufacture  and supply certain probe arrays to  HP for sale in certain markets.
In exchange for  certain rights,  Affymetrix received and  will receive  certain
payments,  including milestones, as defined  research and development objectives
are achieved. In addition, HP will fund certain research work at Affymetrix. The
collaborative agreement is for an initial  five-year term and shall be  extended
thereafter  for consecutive three-year terms, unless either party terminates the
agreement upon  six  months notice.  In  November 1994,  Affymetrix  received  a
license payment from HP that is classified as deferred revenue and as an advance
from  collaborative  partner  in  1995  and  1994,  respectively.  The agreement
contains terms, expiring in November 1996, that allow the payment to be  applied
towards  the purchase of an equity position in Affymetrix upon agreement of both
parties. Affymetrix  is  required to  pay  royalties to  HP  on HP  and  Company
sponsored probe arrays sold by the Company pursuant to the agreement.
 
    In  October 1994,  Affymetrix and  Molecular Dynamics,  Inc. were  awarded a
five-year  matching  grant  for  a  total  of  $31,500,000  under  the  Advanced
Technology  Program within the National Institute of Standards and Technology to
develop a miniaturized DNA diagnostic device, of which approximately $10,700,000
will be available to Molecular  Dynamics. The contract provides that  Affymetrix
will receive funding for approximately
 
                                      F-11
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                    (INFORMATION FOR THE THREE MONTHS ENDED
                   MARCH 31, 1995 AND 1996 AND FOR THE PERIOD
                 FROM INCEPTION TO MARCH 31, 1996 IS UNAUDITED)
 
NOTE 2.  COLLABORATIVE AGREEMENTS AND GRANTS (CONTINUED)
50%  of  its  costs up  to  $20,800,000, some  of  which  will be  used  to fund
activities at  collaborating  academic institutions.  The  award is  subject  to
yearly  congressional authorization,  which is uncertain.  Affymetrix expects to
receive payments monthly based on costs incurred.
 
    Affymetrix  recognized  revenues  of   approximately  $1,412,000  in   1993,
$1,499,000  in 1994, $1,034,000 in 1995, and  $212,000 and $51,000 for the three
months ended March 31, 1995 and 1996, respectively, pursuant to other  contracts
and grants.
 
NOTE 3.  AVAILABLE-FOR-SALE SECURITIES
    The  following is a summary of  available-for-sale securities as of December
31, 1994 (in thousands):
 
<TABLE>
<CAPTION>
                                                                GROSS          GROSS
                                                             UNREALIZED     UNREALIZED     ESTIMATED
                                                   COST         GAINS         LOSSES      FAIR VALUE
                                                 ---------  -------------  -------------  -----------
<S>                                              <C>        <C>            <C>            <C>
U.S. Government obligations....................  $  16,503    $  --          $     382     $  16,121
                                                 ---------          ---            ---    -----------
                                                 ---------          ---            ---    -----------
  Amounts included in:
    cash equivalents...........................  $   4,975    $  --          $  --         $   4,975
    short-term investments.....................     11,528       --                382        11,146
                                                 ---------          ---            ---    -----------
    Total securities...........................  $  16,503    $  --          $     382     $  16,121
                                                 ---------          ---            ---    -----------
                                                 ---------          ---            ---    -----------
</TABLE>
 
    The following is a summary  of available-for-sale securities as of  December
31, 1995 (in thousands):
 
<TABLE>
<CAPTION>
                                                                GROSS          GROSS
                                                             UNREALIZED     UNREALIZED     ESTIMATED
                                                   COST         GAINS         LOSSES      FAIR 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>
 
    The   gross  realized   gains  and  gross   realized  losses   on  sales  of
available-for-sale securities were immaterial for  the years ended December  31,
1994 and 1995.
 
    The following is a summary of the amortized cost and estimated fair value of
available-for-sale  securities at December 31, 1995, by contractual maturity (in
thousands):
 
<TABLE>
<CAPTION>
                                                                              ESTIMATED FAIR
                                                            AMORTIZED COST        VALUE
                                                            --------------  ------------------
<S>                                                         <C>             <C>
Mature in one year or less................................    $   14,184        $   14,184
Mature after one year through three years.................        23,931            24,213
                                                                 -------           -------
  Total...................................................    $   38,115        $   38,397
                                                                 -------           -------
                                                                 -------           -------
</TABLE>
 
NOTE 4.  RELATED PARTY TRANSACTIONS
    In December 1994,  Affymetrix issued a  $6,000,000 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
 
                                      F-12
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                    (INFORMATION FOR THE THREE MONTHS ENDED
                   MARCH 31, 1995 AND 1996 AND FOR THE PERIOD
                 FROM INCEPTION TO MARCH 31, 1996 IS UNAUDITED)
 
NOTE 4.  RELATED PARTY TRANSACTIONS (CONTINUED)
issued  at  $4.50 per  share.  Affymetrix 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 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 Affymetrix  of  certain  financial  covenants to  the  third  party.  In
exchange  for this release, Affymetrix issued  a five-year warrant to Affymax to
purchase 103,382 shares of Series 2 Subordinated convertible preferred stock  at
$5.50 per share.
 
    Effective  January  1, 1993,  Affymetrix entered  into a  Technology License
Agreement with Affymax  whereby Affymetrix  was granted  an exclusive  worldwide
royalty-free  license from  Affymax, with  the right  to sublicense,  to certain
technology and  to certain  future  inventions for  use  in the  diagnostic  and
research  supply markets including uses of DNA probe arrays. In exchange for the
Technology License Agreement and prior Affymax contributions, Affymetrix  issued
Affymax  8,500,000 shares of  Series 1 Subordinated  convertible preferred stock
using a share price of  $1.25, and agreed to  share certain costs of  developing
certain technology.
 
    Two directors of Affymetrix are employees of a subsidiary of Glaxo.
 
    Pursuant   to  a   service  agreement,  Affymax   provided  certain  general
administrative and  legal services  to  Affymetrix from  October 1,  1993  until
December  31, 1994. As  of January 1,  1995, the agreement  was amended to limit
those  services.  Amounts  expensed  by  Affymetrix  under  this  agreement  are
approximately $787,000 in 1993, $806,000 in 1994, $291,000 in 1995, $150,000 for
the  three months ended March 31, 1995, $37,000 for the three months ended March
31, 1996 and $1,921,000  for the period from  inception through March 31,  1996.
General  administrative and legal services were allocated to Affymetrix based on
time spent by Affymax employees exclusively on Affymetrix activities, at a  rate
based  on the  salaries of  the employees involved  plus an  overhead rate. Such
allocation was reasonable in the opinion of Affymetrix management.
 
    Since January 1, 1993, Affymetrix has been occupying a research facility  in
Santa  Clara, California subleased  from Affymax (See  Note 7). Amounts expensed
under this  agreement are  approximately  $275,000 in  1993, $472,000  in  1994,
$529,000  in 1995, $134,000 for the three  months ended March 31, 1995, $134,000
for the three months  ended March 31,  1996 and $1,410,000  for the period  from
inception through March 31, 1996.
 
    Affymetrix  received legal services from Townsend  and Townsend and Crew LLP
("Townsend") related  to  the  intellectual property  rights  of  Affymetrix.  A
partner  of Townsend was  also an employee  on a part  time basis of Affymetrix.
Legal expenses  related  to services  performed  by Townsend  are  approximately
$85,000  in 1993,  $369,000 in  1994, $612,000 in  1995, $144,000  for the three
months ended March 31, 1995, $193,000 for the three months ended March 31,  1996
and $1,259,000 for the period from inception through March 31, 1996.
 
   
    In  June 1993, the Board  approved the issuance of  secured loans to certain
officers for  a total  of $80,000  at an  interest rate  of 5.07%  per year  and
payable  in  full  at  the  earlier  of July  1,  1998  or  upon  termination of
employment. The  loans  were  originally  recorded  as  "notes  receivable  from
officers"  in  shareholders' equity.  In  June 1995,  one  loan for  $40,000 was
reclassified to "other assets". In November 1994, the Board agreed to  authorize
$117,000  as collateral  to a bank  for an  officer's loan. In  August 1995, the
Board approved the issuance  of a five-year  secured loan to  an employee for  a
total  of $50,000 at an interest rate of 8%  per year and payable in full at the
earlier of October 2, 2000 or upon termination of employment.
    
 
                                      F-13
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                    (INFORMATION FOR THE THREE MONTHS ENDED
                   MARCH 31, 1995 AND 1996 AND FOR THE PERIOD
                 FROM INCEPTION TO MARCH 31, 1996 IS UNAUDITED)
 
NOTE 5.  NOTES PAYABLE AND CREDIT ARRANGEMENTS
 
NOTES PAYABLE
 
    In December 1994,  Affymetrix issued a  $6,000,000 subordinated  convertible
promissory  note to Affymax maturing on December 1, 1997, which was subsequently
converted into 1,333,333 shares of  Series B Senior convertible preferred  stock
in August 1995 at a conversion rate of $4.50 per share (See Note 4).
 
CREDIT ARRANGEMENTS
 
    In  December 1994,  Affymetrix entered into  a financing  arrangement with a
leasing company for existing equipment. Under the terms of the lease, Affymetrix
received a single minimum aggregate lease payment of $1,307,000 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 $1,761,000 with  accumulated depreciation of $464,000 and  $818,000
at  December 31, 1994 and December  31, 1995, respectively. Amortization of this
property and equipment is included in depreciation expense. Future minimum lease
payments under the capital lease obligation at December 31, 1995 are as  follows
(in thousands):
 
<TABLE>
<S>                                                           <C>
1996........................................................  $     292
1997........................................................        292
1998........................................................        292
1999........................................................        291
2000........................................................        280
                                                              ---------
Total minimum lease payments................................      1,447
Less amount representing interest...........................       (312)
                                                              ---------
Present value of minimum lease payments.....................      1,135
Less current portion........................................       (187)
                                                              ---------
Noncurrent obligation under capital lease...................  $     948
                                                              ---------
                                                              ---------
</TABLE>
 
NOTE 6.  SHAREHOLDERS' EQUITY
 
PREFERRED SHARES
 
    Affymetrix  is  authorized to  issue 27,500,000  shares of  preferred stock,
designated as  follows:  6,000,000 for  Series  A Senior  convertible  preferred
stock;  8,666,666 for Series B Senior convertible preferred stock; 8,500,000 for
Series 1  Subordinated  convertible  preferred stock;  1,000,000  for  Series  2
Subordinated preferred stock and 3,333,334 shares undesignated.
 
    The following table describes information with respect to the various series
of convertible preferred stock outstanding as of December 31, 1994:
 
<TABLE>
<CAPTION>
                                                                                      TOTAL
                                                 SHARES ISSUED   ISSUANCE PRICE    LIQUIDATION
                                                AND OUTSTANDING     PER SHARE      PREFERENCE
                                                ---------------  ---------------  -------------
<S>                                             <C>              <C>              <C>
Series A......................................       6,000,000      $    3.50     $  21,000,000
Series 1......................................       8,500,000           1.25        10,625,000
                                                ---------------                   -------------
                                                    14,500,000                    $  31,625,000
                                                ---------------                   -------------
                                                ---------------                   -------------
</TABLE>
 
                                      F-14
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                    (INFORMATION FOR THE THREE MONTHS ENDED
                   MARCH 31, 1995 AND 1996 AND FOR THE PERIOD
                 FROM INCEPTION TO MARCH 31, 1996 IS UNAUDITED)
 
NOTE 6.  SHAREHOLDERS' EQUITY (CONTINUED)
    The following table describes information with respect to the various series
of convertible preferred stock outstanding as of December 31, 1995 and March 31,
1996:
 
<TABLE>
<CAPTION>
                                                                                      TOTAL
                                                 SHARES ISSUED   ISSUANCE PRICE    LIQUIDATION
                                                AND OUTSTANDING     PER SHARE      PREFERENCE
                                                ---------------  ---------------  -------------
<S>                                             <C>              <C>              <C>
Series A......................................       6,000,000      $    3.50     $  21,000,000
Series B......................................       8,666,666           4.50        39,000,000
Series 1......................................       8,500,000           1.25        10,625,000
                                                ---------------                   -------------
                                                    23,166,666                    $  70,625,000
                                                ---------------                   -------------
                                                ---------------                   -------------
</TABLE>
 
    The  Series A  and Series B  Senior and  Series 1 and  Series 2 Subordinated
convertible  shares  represent   convertible  noncumulative  preferred   shares.
Dividends  for  Series  A  and  B  are  payable  at  $.28  and  $.36  per share,
respectively, in  preference  to  payment  of any  dividends  on  the  Series  1
Subordinated preferred shares, Series 2 Subordinated preferred shares and common
stock,  when and  if declared  by the Board.  Dividends for  Series 1  and 2 are
payable at $.10 and $.44 per  share, respectively. In the event of  liquidation,
dissolution,  or winding  up of  Affymetrix, the  Series A  and Series  B Senior
preferred  shares  will  have  a  liquidation  preference  over  the  Series   1
Subordinated preferred shares, Series 2 Subordinated preferred shares and common
stock. Each share of preferred stock is entitled to the number of votes equal to
the  number of shares of  common stock into which  such share of preferred stock
could be  converted.  Each share  of  preferred  stock is  convertible,  at  the
holder's  option, into  0.6667 share  of common  stock subject  to anti-dilution
adjustment upon the issuance of additional shares of common stock as defined  in
Affymetrix' Articles of Incorporation (See Note 9).
 
    The  Series A  Senior preferred  shares, Series  B Senior  preferred shares,
Series 1  Subordinated  preferred shares  and  Series 2  Subordinated  preferred
shares will be automatically converted (i) upon the closing of a firm commitment
underwritten  public offering  pursuant to  an effective  registration statement
under the Securities Act  of 1933, as  amended, covering the  offer and sale  of
common  stock  to  the  public  at  an  aggregate  offering  price  of  at least
$7,500,000; (ii) immediately upon receipt by Affymetrix of a written request for
conversion of at least  60% of the  then outstanding shares  of that series;  or
(iii)  upon the  conversion of at  least 60% of  the shares of  that series ever
outstanding.
 
STOCK WARRANTS
 
    At December  31,  1995,  the  following  warrants  to  purchase  Affymetrix'
preferred stock were outstanding:
 
<TABLE>
<CAPTION>
                                                            EXERCISE     NUMBER OF                   EXPIRATION
                                                              PRICE       SHARES      ISSUE DATE        DATE
                                                           -----------  -----------  -------------  -------------
<S>                                                        <C>          <C>          <C>            <C>
Series 2 Subordinated convertible preferred..............   $    5.50      103,382          1994           1999
Series 2 Subordinated convertible preferred..............   $    5.50      202,441          1995           2000
</TABLE>
 
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.
 
                                      F-15
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                    (INFORMATION FOR THE THREE MONTHS ENDED
                   MARCH 31, 1995 AND 1996 AND FOR THE PERIOD
                 FROM INCEPTION TO MARCH 31, 1996 IS UNAUDITED)
 
NOTE 6.  SHAREHOLDERS' EQUITY (CONTINUED)
    Activity under the Stock Plan through March 31, 1996 is as follows:
 
<TABLE>
<CAPTION>
                                                                         OUTSTANDING OPTIONS
                                                                --------------------------------------
                                                                NUMBER OF    PRICE PER     AGGREGATE
                                                                  SHARES       SHARE         PRICE
                                                                ----------  ------------  ------------
<S>                                                             <C>         <C>           <C>
Options granted...............................................     714,081  $       0.30  $    214,224
Options exercised.............................................    (333,332)         0.30      (100,000)
                                                                ----------  ------------  ------------
  Balance at December 31, 1993................................     380,749          0.30       114,224
Options granted...............................................     634,238    0.30-0.675       331,547
Options exercised.............................................     (74,200)         0.30       (22,260)
Options canceled..............................................     (38,799)         0.30       (11,640)
                                                                ----------  ------------  ------------
  Balance at December 31, 1994................................     901,988    0.30-0.675       411,871
Options granted...............................................   1,423,917         0.675       961,144
Options exercised.............................................     (62,749)   0.30-0.675       (22,524)
Options canceled..............................................    (104,032)   0.30-0.675       (56,597)
                                                                ----------  ------------  ------------
  Balance at December 31, 1995................................   2,159,124    0.30-0.675     1,293,894
Options granted...............................................     107,500    0.675-4.80       173,281
Options exercised.............................................     (72,973)   0.30-0.675       (45,627)
Options cancelled.............................................      (2,133)   0.30-0.675          (690)
                                                                ----------  ------------  ------------
  Balance at March 31, 1996...................................   2,191,518  $  0.30-4.80  $  1,420,858
                                                                ----------  ------------  ------------
                                                                ----------  ------------  ------------
</TABLE>
 
    At December 31, 1995 and March 31, 1996, options for the purchase of 219,446
and 158,490  shares  were exercisable,  respectively,  and 148,889  shares  were
subject to repurchase.
 
    For  options  granted through  December 31,  1995, Affymetrix  recognized an
aggregate of $2,488,000 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.  Deferred
compensation  related to options granted during the three months ended March 31,
1996 was $326,000. The  deferred compensation expense  is being recognized  over
the vesting period of the options.
 
    Affymetrix  employees  have participated  in  the Affymax  stock  option and
benefit plan. The Affymax stock option plan, employees stock purchase plan,  and
investment  savings  plan have  had  no impact  on  the financial  statements of
Affymetrix.
 
NOTE 7.  OPERATING LEASE COMMITMENTS
    Since January 1, 1993, Affymetrix has been occupying a research facility  in
Santa  Clara, California leased by Affymax. In February 1994, Affymetrix entered
into a noncancelable operating  sublease agreement with Affymax  for a 21  month
period.  Affymetrix obtained an  extension through October  1996. The underlying
lease contains an option to renew the lease for an additional term of 82 months.
 
    In December 1994,  Affymetrix entered into  a noncancelable five-year  lease
for  the rental of a manufacturing facility in Sunnyvale, California. Affymetrix
has options to renew the lease for two additional three-year terms.
 
                                      F-16
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                    (INFORMATION FOR THE THREE MONTHS ENDED
                   MARCH 31, 1995 AND 1996 AND FOR THE PERIOD
                 FROM INCEPTION TO MARCH 31, 1996 IS UNAUDITED)
 
NOTE 7.  OPERATING LEASE COMMITMENTS (CONTINUED)
    In  October  1995,  Affymetrix  entered  into  a  four-year  lease,  and   a
noncancelable  17 month sublease,  for the rental of  a research and development
facility in Sunnyvale, California.
 
    Future minimum  rental  payments  under noncancelable  operating  leases  at
December 31, 1995 are as follows (in thousands):
 
<TABLE>
<S>                                                           <C>
1996........................................................  $   1,102
1997........................................................      1,042
1998........................................................      1,039
1999........................................................      1,099
2000........................................................        688
Thereafter..................................................      1,664
                                                              ---------
Total minimum rental payments...............................  $   6,634
                                                              ---------
                                                              ---------
</TABLE>
 
    Rent expense related to operating leases was approximately $275,000 in 1993,
$472,000  in 1994, $664,000 in 1995 and $2,005,000 for the period from inception
through December 31, 1995.
 
    Affymetrix entered into certain  noncancelable obligations for the  purchase
of  GeneChip equipment and supplies. The  maximum commitment under the contracts
at December 31, 1995 is $1,735,000, which will be paid as units are received  in
1996.
 
NOTE 8.  INCOME TAXES
    As  of December 31, 1995, Affymetrix has net operating loss carryforwards of
approximately $22,000,000, which will expire at various dates beginning on  2008
through 2010, 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 Affymetrix deferred  tax assets as of December  31
are as follows (in thousands):
 
<TABLE>
<CAPTION>
                                                                  1993       1994       1995
                                                                ---------  ---------  ---------
<S>                                                             <C>        <C>        <C>
Net operating loss carryforwards..............................  $   1,733  $   4,284  $   8,063
Research credits..............................................        346        708      1,167
Deferred revenue..............................................        156        710      1,041
Other-net.....................................................          7        209        532
                                                                ---------  ---------  ---------
Total deferred tax assets.....................................      2,242      5,911     10,803
Valuation allowance for deferred tax assets...................     (2,242)    (5,911)   (10,803)
                                                                ---------  ---------  ---------
Net deferred tax assets.......................................  $  --      $  --      $  --
                                                                ---------  ---------  ---------
                                                                ---------  ---------  ---------
</TABLE>
 
    The  valuation allowance increased by $2,163,000, $3,669,000, and $4,892,000
during 1993, 1994, and 1995, respectively.
 
NOTE 9.  OTHER EVENTS SUBSEQUENT TO DECEMBER 31, 1995
   
    On March 7, 1996,  the Board of Directors  approved a two-for-three  reverse
stock  split  of  its common  stock  through  an amendment  to  its  Articles of
Incorporation. The  reverse stock  split  was effective  on  May 20,  1996.  All
    
 
                                      F-17
<PAGE>
                                AFFYMETRIX, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
 
                    (INFORMATION FOR THE THREE MONTHS ENDED
                   MARCH 31, 1995 AND 1996 AND FOR THE PERIOD
                 FROM INCEPTION TO MARCH 31, 1996 IS UNAUDITED)
 
NOTE 9.  OTHER EVENTS SUBSEQUENT TO DECEMBER 31, 1995 (CONTINUED)
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
also  been retroactively adjusted to reflect the  reverse stock split as well as
the anti-dilution adjustment.  As of the  effective date of  the offering it  is
estimated  that each share  of Series A,  Series B and  Series 1 preferred stock
will convert  into approximately  0.6823, 0.6667,  and 0.6775  shares of  common
stock, respectively.
 
    In  addition,  on  March 7,  1996,  the  Board authorized  the  filing  of a
registration statement with  the Securities and  Exchange Commission  permitting
Affymetix  to sell shares of its common stock  to the public. If the offering is
consummated  under  the  terms  presently  anticipated,  all  of  the  currently
outstanding preferred stock will automatically convert into 15,629,991 shares of
common  stock and the warrants will be  exercisable for 203,881 shares of common
stock at $8.25 per share. Unaudited pro forma shareholders' equity, as  adjusted
for  the conversion  of the  preferred stock, is  set forth  in the accompanying
balance sheets.
 
   
    In  April  1996,   Affymetrix  entered   into  an   agreement  with   Incyte
Pharmaceuticals,  Inc. to explore potential uses of DNA probe arrays in the area
of gene expression.  As a result  of this agreement,  Affymetrix is required  to
refund  30% of the development funding received from GI, and future funding from
GI will be proportionally reduced. The Company has recorded an accrued liability
for this refund. (See Notes 1 and 2).
    
 
    In May 1996, Affymetrix entered into an agreement with Glaxo to design, test
and  supply  probe  arrays  to  demonstrate  use  of  the  arrays  in  detecting
polymorphisms  in specific  genes. Glaxo and  Affymetrix will design  and test a
probe array  containing genes  specified by  Glaxo. If  successfully  developed,
Affymetrix  will supply Glaxo's  requirements of such  probe arrays for research
purposes.
 
                                      F-18
<PAGE>
Affymetrix GeneChip Probe Array Manufacturing
- -----------------------------------
 
<TABLE>
<S>                                      <C>
             Combinationatorial                         [PICTURE]
             Synthesis
              Affymetrix is able to
              synthesize tens of
              thousands of different
              DNA probes in parallel. A
              robotic arm is shown
              transporting a wafer on a
              synthesizer.
 
               [PICTURE]                 Photolithography
                                         Affymetrix manufactures wafers of
                                         GeneChip 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.
 
Wafer-Scale Production                                  [PICTURE]
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.
</TABLE>
 
<PAGE>
                                     [LOGO]
<PAGE>
                                    PART II
                     INFORMATION NOT REQUIRED IN PROSPECTUS
 
ITEM 13.  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 of the  Common Stock being registered.  All amounts are estimated
except the SEC  Registration Fee, the  NASD Filing Fee  and the Nasdaq  National
Market Application Fee.
 
   
<TABLE>
<S>                                                                 <C>
SEC Registration Fee..............................................  $  30,932
NASD Filing Fee...................................................      9,470
Nasdaq National Market Application Fee............................     50,000
Blue Sky Qualification Fees and Expenses..........................     10,000
Accounting Fees and Expenses......................................    150,000
Legal Fees and Expenses (including Blue Sky)......................    300,000
Transfer Agent and Registrar Fees.................................      5,000
Printing and Engraving............................................    150,000
Miscellaneous.....................................................     94,598
                                                                    ---------
    Total.........................................................  $ 800,000
                                                                    ---------
                                                                    ---------
</TABLE>
    
 
ITEM 14.  INDEMNIFICATION OF DIRECTORS AND OFFICERS
 
    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, 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 expense 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,  judgment, fines settlement 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  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
 
                                      II-1
<PAGE>
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 15.  RECENT SALES OF UNREGISTERED SECURITIES
 
    During  the past three  years, the registrant has  issued the securities set
forth below  which were  not registered  under the  Securities Act  of 1933,  as
amended (the "Act"). The share amounts (and purchase and option exercise prices)
set  forth below have been adjusted to  give effect to the two-for-three reverse
stock split of the Common Stock effected in  May 1996 but do not give effect  to
the  conversion of Preferred  Stock into Common  Stock upon the  closing of this
offering.
 
    (1) COMMON STOCK.   In August  1993, the registrant  issued to Affymax  N.V.
("Affymax"),  an accredited  investor, 667 shares  of Common Stock  at $0.15 per
share. The  issuance was  a  private placement  without general  advertising  or
solicitation to an "accredited investor" within the meaning of Rule 501(a) under
the  Act and was  exempt from registration  under Section 4(2)  of the Act. From
December 1993 to April 30, 1996, the registrant issued 552,169 shares of  Common
Stock  at  prices  ranging between  $0.30  per  share and  $0.675  per  share to
directors, employees and  consultants in  connection with the  exercise by  such
directors,  employees  and  consultants  of  stock  options  held  by  them. All
issuances made  pursuant  to  the  exercise  of  options  were  made  under  the
registrant's  1993 Stock Plan, as amended. In August 1995, the registrant issued
65,320 shares of Common  Stock for financing commissions.  All of the  foregoing
issuances  and exercises  of options were  exempt from  registration pursuant to
Section 3(b) of the Act and Rule 701 promulgated thereunder.
 
    (2) SERIES A  SENIOR CONVERTIBLE PREFERRED  STOCK.  In  September 1993,  the
registrant  sold an aggregate of 6,000,000 shares of Series A Convertible Senior
Preferred Stock for $3.50  per share to  approximately 48 accredited  investors.
The sales were private placements without general advertising or solicitation to
"accredited  investors" within the meaning of Rule 501(a) under the Act and were
exempt from registration under Section 4(2) of the Act.
 
    (3) SERIES  B SENIOR  CONVERTIBLE  PREFERRED STOCK.    In August  1995,  the
registrant  sold 8,666,666 shares of Series B Senior Convertible Preferred Stock
at a price  of $4.50 per  share to approximately  100 accredited investors.  The
sales  were private  placements without  general advertising  or solicitation to
"accredited investors" within the meaning of Rule 501(a) under the Act and  were
exempt from registration under Section 4(2) of the Act.
 
    (4)  SERIES 1 SUBORDINATED  CONVERTIBLE PREFERRED STOCK.   In September 1993
the registrant  issued to  Affymax  8,500,000 shares  of Series  1  Subordinated
Preferred  Stock at a price of $1.25 per share. The sale was a private placement
without general advertising or solicitation  to an "accredited investor"  within
the  meaning of Rule 501(a) under the Act and was exempt from registration under
Section 4(2) of the Act.
 
    (5)  WARRANTS  TO  PURCHASE  SERIES  2  SUBORDINATED  CONVERTIBLE  PREFERRED
STOCK.   In December 1994, the registrant issued a five-year warrant to purchase
an aggregate of 103,382 shares of Series 2 Subordinated
 
                                      II-2
<PAGE>
Convertible Preferred  Stock  exercisable  at  $5.50 per  share  to  Affymax  in
consideration  for relieving the  Company of certain  financial covenants and to
guarantee its  obligation to  a  third party.  In  1995, the  registrant  issued
five-year  warrants  to purchase  an  aggregate of  202,441  shares of  Series 2
Subordinated Convertible  Preferred  Stock exercisable  at  $5.50 per  share  to
Affymax  in consideration for certain interest  payments otherwise due on a note
agreement. Affymax is an "accredited investor" within the meaning of Rule 501(a)
under the Act. The sales were private placements without general advertising  or
solicitation and was exempt from registration under Section 4(2) of the Act.
 
    (6)    OPTION    ISSUANCES   TO    DIRECTORS,   OFFICERS,    EMPLOYEES   AND
CONSULTANTS.   From July  1993 to  April  30, 1996,  the registrant  has  issued
options  to purchase a total of 2,885,400  shares of Common Stock at an exercise
price ranging  between  $0.30  and  $4.80  per  share  to  directors,  officers,
employees  and  consultants.  As of  the  date of  this  registration statement,
552,169 options have been exercised. All  of such issuances were made under  the
registrant's  1993  Stock Plan,  as amended.  No consideration  was paid  to the
registrant by any recipient of any of the foregoing options for the grant of any
such options. All  of the  foregoing issuances  and exercises  were exempt  from
registration  pursuant  to Section  3(b)  of the  Act  and Rule  701 promulgated
thereunder.
 
ITEM 16.  EXHIBITS AND FINANCIAL STATEMENT SCHEDULES
 
    (a)  Exhibits
 
   
<TABLE>
<C>        <S>
    **1.1  Form of Underwriting Agreement
    **3.1  Amended and Restated Articles of Incorporation
    **3.2  Form of Amended and Restated Articles, to be effective upon closing
    **3.3  Bylaws
    **3.4  Form of Certificate of Amendment of Amended and Restated Articles of
            Incorporation
    **4.1  Specimen Common Stock Certificate
    **5.1  Opinion of Heller Ehrman White & McAuliffe
   **10.1  1993 Stock Plan, as amended
   **10.2  1996 Nonemployee Directors Stock Option Plan
    +10.3  Collaboration Agreement by and between Hewlett-Packard Company and Affymetrix,
            Inc. dated November 11, 1994
    +10.4  Development and Supply Agreement between Affymetrix, Inc. and Genetics
            Institute, Inc. dated November 15, 1994
    +10.5  Supply Agreement with Genetics Institute, Inc. dated December 8, 1995
  **+10.6  Technology License Agreement among Affymax N.V., Affymax Technologies, N.V.,
            the Affymax Research Institute, and Affymetrix, Inc. dated January 1, 1993
   **10.7  Severance Agreement and Release between Affymetrix, Inc. and David B. Singer
            dated June 15, 1995
   **10.8  Loan and Pledge Agreement between David B. Singer and Affymetrix, Inc.
            effective December 7, 1993.
  **+10.9  ATP Participation Agreement between Affymetrix, Inc. and Molecular Dynamics,
            Inc. dated January 12, 1995 pursuant to the National Institute of Standards
            and Technology's Advanced Technology Program.
  **10.10  Amendment 1 to the ATP Participation Agreement between Affymetrix, Inc. and
            Molecular Dynamics, Inc. effective January 13, 1996.
 **+10.11  Governance Agreement between Affymetrix, Inc. and Glaxo Wellcome plc dated
            July 6, 1995.
  **10.12  Services Agreement between Affymax Research Institute and Affymetrix, Inc.
            effective October 1, 1993.
</TABLE>
    
 
                                      II-3
<PAGE>
   
<TABLE>
<C>        <S>
  **10.13  Loan Agreement between Affymax Technologies N.V. and Affymetrix, Inc. dated
            December 1, 1994.
  **10.14  Lease between Solar Oakmead Joint Venture and Affymetrix, Inc. dated October
            20, 1995.
  **10.15  Sublease between Salutar, Inc. and Affymetrix, Inc. dated October 20, 1995.
  **10.16  Sublease between Affymax Research Institute and Affymetrix, Inc. dated
            February 1, 1994.
 **+10.17  Manufacturing and Supply Agreement between Affymetrix, Inc. and RELA, Inc.
            dated November 27, 1995.
  **10.18  Loan and Pledge Agreement between Stephen P.A. Fodor and Affymetrix, Inc.
            effective December 7, 1993.
  **10.19  Agreement between Stephen P.A. Fodor and Affymetrix, Inc. dated November 1,
            1994.
  **10.20  Form of Director and Officer Indemnification Agreement
 **+10.21  Demonstration Agreement between Affymetrix, Inc. and Glaxo Wellcome, Inc.
            dated May 1, 1996
  **10.22  Lease between Harry Locklin and Affymetrix, Inc. dated December 5, 1994.
   **11.1  Statement of computation of net loss per share
     23.1  Consent of Ernst & Young LLP, independent auditors
   **23.2  Consent of Heller Ehrman White & McAuliffe
     23.3  Consent of Townsend and Townsend and Crew LLP
   **24.1  Power of Attorney (included on page II-5)
   **24.2  Power of Attorney of Alejandro C. Zaffaroni
   **24.3  Power of Attorney of Barry C. Ross
</TABLE>
    
 
- ------------
**  Previously filed.
 +  Confidential treatment requested.
 
ITEM 17.  UNDERTAKINGS
    A.  The  undersigned  registrant  hereby   undertakes  to  provide  to   the
underwriter   at  the   closing  specified   in  the   underwriting  agreements,
certificates in such denominations and registered  in such names as required  by
the underwriter to permit prompt delivery to each purchaser.
 
    B.  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  provisions  described  in Item  14  above, 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 of  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.
 
    C. The undersigned registrant hereby undertakes that:
 
    (1) 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 of 1933 shall be deemed to be part of this registration
statement as of the time it was declared effective.
 
    (2) 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.
 
                                      II-4
<PAGE>
                                   SIGNATURE
 
   
    Pursuant to the requirements of the Securities Act of 1933, Affymetrix, Inc.
has duly caused this Amendment No. 3 to Registration Statement on Form S-1 to be
signed  on its  behalf by the  undersigned, thereunto duly  authorized, in Santa
Clara, California on June 3, 1996.
    
 
                                          AFFYMETRIX, INC.
                                          By                  *
 
                                            ------------------------------------
                                             JOHN D. DIEKMAN, Ph.D.
                                            CHIEF EXECUTIVE OFFICER AND CHAIRMAN
 
    Pursuant  to  the  requirements  of   the  Securities  Act  of  1933,   this
Registration  Statement on Form S-1 has been  signed by the following persons in
the capacities and on the dates indicated.
 
   
<TABLE>
<CAPTION>
                      SIGNATURE                                        CAPACITY                        DATE
- -----------------------------------------------------  -----------------------------------------  ---------------
 
<C>                                                    <S>                                        <C>
                                    *                  Director, and Chief Executive
     ------------------------------------------         Officer (Principal Executive Officer)      June 3, 1996
               John D. Diekman, Ph.D.
 
                                    *
     ------------------------------------------        Director and President                      June 3, 1996
              Stephen P.A. Fodor, Ph.D.
 
                                    *
     ------------------------------------------        Director                                    June 3, 1996
                  Paul Berg, Ph.D.
 
                                    *
     ------------------------------------------        Director                                    June 3, 1996
                   Douglas M. Hurt
 
                                    *
     ------------------------------------------        Director                                    June 3, 1996
                Vernon R. Loucks, Jr.
 
                                    *
     ------------------------------------------        Director                                    June 3, 1996
                Barry C. Ross, Ph.D.
 
                                    *
     ------------------------------------------        Director                                    June 3, 1996
                   David B. Singer
 
                                    *
     ------------------------------------------        Director                                    June 3, 1996
                    John A. Young
 
                                    *
     ------------------------------------------        Director                                    June 3, 1996
            Alejandro C. Zaffaroni Ph.D.
 
                  /s/ KENNETH J. NUSSBACHER            Chief Financial Officer
     ------------------------------------------         (Principal Financial and                   June 3, 1996
                Kenneth J. Nussbacher                   Accounting Officer)
 
        *By:       /s/ KENNETH J. NUSSBACHER
          -------------------------------------                                                    June 3, 1996
                  Kenneth J. Nussbacher
                   (ATTORNEY-IN-FACT)
</TABLE>
    
 
                                      II-5
<PAGE>
                               INDEX TO EXHIBITS
 
   
<TABLE>
<CAPTION>
 EXHIBIT                                                                                              PAGE
- ----------                                                                                          ---------
 
<C>         <S>                                                                                     <C>
    **1.1   Form of Underwriting Agreement........................................................
 
    **3.1   Amended and Restated Articles of Incorporation........................................
 
    **3.2   Amended and Restated Articles, to be effective upon closing...........................
 
    **3.3   Bylaws................................................................................
 
    **3.4   Form of Certificate of Amendment of Amended and Restated Articles of Incorporation....
 
    **4.1   Specimen Common Stock Certificate.....................................................
 
    **5.1   Opinion of Heller Ehrman White & McAuliffe............................................
 
   **10.1   1993 Stock Plan, as amended...........................................................
 
   **10.2   1996 Nonemployee Directors Stock Option Plan..........................................
 
    +10.3   Collaboration Agreement by and between Hewlett-Packard Company and Affymetrix, Inc.
            dated November 11, 1994...............................................................
 
    +10.4   Development and Supply Agreement between Affymetrix, Inc. and Genetics Institute, Inc.
            dated November 15, 1994...............................................................
 
    +10.5   Supply Agreement with Genetics Institute, Inc. dated December 8, 1995.................
 
  **+10.6   Technology License Agreement among Affymax N.V., Affymax Technologies, N.V., the
            Affymax Research Institute, and Affymetrix, Inc. dated January 1, 1993................
 
   **10.7   Severance Agreement and Release between Affymetrix, Inc. and David B. Singer dated
            June 15, 1995.........................................................................
 
   **10.8   Loan and Pledge Agreement between David B. Singer and Affymetrix, Inc. effective
            December 7, 1993......................................................................
 
  **+10.9   ATP Participation Agreement between Affymetrix, Inc. and Molecular Dynamics, Inc.
            dated January 12, 1995 pursuant to the National Institute of Standards and
            Technology's Advanced Technology Program..............................................
 
   **10.10  Amendment 1 to the ATP Participation Agreement between Affymetrix, Inc. and Molecular
            Dynamics, Inc. effective January 13, 1996.............................................
 
  **+10.11  Governance Agreement between Affymetrix, Inc. and Glaxo Wellcome plc dated July 6,
            1995..................................................................................
 
   **10.12  Services Agreement between Affymax Research Institute and Affymetrix, Inc. effective
            October 1, 1993.......................................................................
 
   **10.13  Loan Agreement between Affymax Technologies N.V. and Affymetrix, Inc. dated December
            1, 1994...............................................................................
 
   **10.14  Lease between Solar Oakmead Joint Venture and Affymetrix, Inc. dated October 20,
            1995..................................................................................
 
   **10.15  Sublease between Salutar, Inc. and Affymetrix, Inc. dated October 20, 1995............
 
   **10.16  Sublease between Affymax Research Institute and Affymetrix, Inc. dated February 1,
            1994..................................................................................
 
  **+10.17  Manufacturing and Supply Agreement between Affymetrix, Inc. and RELA, Inc. dated
            November 27, 1995.....................................................................
</TABLE>
    
<PAGE>
   
<TABLE>
<C>         <S>                                                                                     <C>
   **10.18  Loan and Pledge Agreement between Stephen P.A. Fodor and Affymetrix, Inc. effective
            December 7, 1993......................................................................
 
   **10.19  Agreement between Stephen P.A. Fodor and Affymetrix, Inc. dated November 1, 1994......
 
   **10.20  Form of Director and Officer Indemnification Agreement................................
 
  **+10.21  Demonstration Agreement between Affymetrix, Inc. and Glaxo Wellcome, Inc. dated May 1,
            1996..................................................................................
 
   **10.22  Lease between Harry Locklin and Affymetrix, Inc. dated December 5, 1994...............
 
   **11.1   Statement of computation of loss per share............................................
 
     23.1   Consent of Ernst & Young LLP, independent auditors....................................
 
   **23.2   Consent of Heller Ehrman White & McAuliffe............................................
 
     23.3   Consent of Townsend and Townsend and Crew LLP.........................................
 
   **24.1   Power of Attorney (included on page II-5).............................................
 
   **24.2   Power of Attorney of Alejandro C. Zaffaroni...........................................
 
   **24.3   Power of Attorney of Barry C. Ross....................................................
</TABLE>
    
 
- ------------
**  Previously filed.
 +  Confidential treatment requested.
<PAGE>
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
                       SECURITIES AND EXCHANGE COMMISSION
 
                             WASHINGTON, D.C. 20549
 
                            ------------------------
 
                                    EXHIBITS
                                       TO
                                    FORM S-1
 
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
 
                            ------------------------
 
                                AFFYMETRIX, INC.
 
                                    VOLUME I
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>
- ---------------------------------------------------------
- ---------------------------------------------------------
 
                       SECURITIES AND EXCHANGE COMMISSION
 
                             WASHINGTON, D.C. 20549
 
                            ------------------------
 
                                    EXHIBITS
                                       TO
                                    FORM S-1
 
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
 
                            ------------------------
 
                                AFFYMETRIX, INC.
 
                                   VOLUME II
 
- ---------------------------------------------------------
- ---------------------------------------------------------

<PAGE>


              CONFIDENTIAL TREATMENT REQUESTED BY AFFYMETRIX, INC.




                             COLLABORATION AGREEMENT

                                 BY AND BETWEEN

                            HEWLETT-PACKARD COMPANY

                                       AND

                                AFFYMETRIX, INC.

                             DATED NOVEMBER 11, 1994


<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED


                                TABLE OF CONTENTS

1.  BASIC PRINCIPLES OF THE COLLABORATION. . . . . . . . . . . . . . . . . .   1
    1.1.  INTENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   1
    1.2.  MUTUALLY PROFITABLE. . . . . . . . . . . . . . . . . . . . . . . .   1
    1.3.  ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . .   1
    1.4.  PRE-EXISTING IP. . . . . . . . . . . . . . . . . . . . . . . . . .   1
    1.5.  NEW PRODUCTS AND NEW USES. . . . . . . . . . . . . . . . . . . . .   1
    1.6.  EXPERIENCES OF MTX . . . . . . . . . . . . . . . . . . . . . . . .   2
    1.7.  EXPERIENCES OF HP. . . . . . . . . . . . . . . . . . . . . . . . .   2
    1.8.  HP MARKET. . . . . . . . . . . . . . . . . . . . . . . . . . . . .   2
    1.9.  MTX MARKET . . . . . . . . . . . . . . . . . . . . . . . . . . . .   2
    1.10. EFFORTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   2
    1.11. FUNDING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   2
    1.12. SUPPLY PRICE . . . . . . . . . . . . . . . . . . . . . . . . . . .   2

2.  DEFINITIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   2
    2.1.  "AFFILIATE". . . . . . . . . . . . . . . . . . . . . . . . . . . .   2
    2.2.  "ARRAY READER" . . . . . . . . . . . . . . . . . . . . . . . . . .   2
    2.3.  "BACKGROUND IPR" . . . . . . . . . . . . . . . . . . . . . . . . .   2
    2.4.  "BETA MODEL" . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
    2.5.  [  * ] CHIPS . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
    2.6.  "DNA CHIP" . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
    2.7.  "EMERGING COMPANIES" . . . . . . . . . . . . . . . . . . . . . . .   3
    2.8.  "HP CHIP". . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
    2.9.  "HP SOFTWARE". . . . . . . . . . . . . . . . . . . . . . . . . . .   3
    2.10. "HP SYSTEM". . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
    2.11. "INTELLECTUAL PROPERTY RIGHTS" ("IPR") . . . . . . . . . . . . . .   3
    2.12. "INVENTION". . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
    2.13. "MATERIAL BREACH". . . . . . . . . . . . . . . . . . . . . . . . .   3
    2.14. "MTX CHIP" . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
    2.15. "MTX SOFTWARE" . . . . . . . . . . . . . . . . . . . . . . . . . .   4
    2.16. "MTX SPONSORED CHIP" . . . . . . . . . . . . . . . . . . . . . . .   4
    2.17. "NECESSARY REAGENTS" . . . . . . . . . . . . . . . . . . . . . . .   4
    2.18. "NET SALES". . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
    2.19. "PATENT APPLICATION" . . . . . . . . . . . . . . . . . . . . . . .   4
    2.20. "PROSECUTE". . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
    2.21. "PRODUCTION MODEL" . . . . . . . . . . . . . . . . . . . . . . . .   4
    2.22. "PRODUCTS" . . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
    2.23. "RESIDUAL KNOWLEDGE" . . . . . . . . . . . . . . . . . . . . . . .   4
    2.24. "TYPE OF CHIP" . . . . . . . . . . . . . . . . . . . . . . . . . .   5
    2.25. "WORKPLAN" . . . . . . . . . . . . . . . . . . . . . . . . . . . .   5

3.  MARKET SEGMENT DEFINITIONS--NON-CLINICAL MARKET. . . . . . . . . . . . .   5
    3.1.  BIOANALYTICAL MARKET . . . . . . . . . . . . . . . . . . . . . . .   5


                                        
<PAGE>

    3.2.  BIOMEDICAL RESEARCH MARKET . . . . . . . . . . . . . . . . . . . .   5
    3.3.  DUAL-NATURE ACCOUNTS . . . . . . . . . . . . . . . . . . . . . . .   5
          3.3.1.  DEFINITION . . . . . . . . . . . . . . . . . . . . . . . .   5
          3.3.2.  ESTABLISHING ACCOUNTS. . . . . . . . . . . . . . . . . . .   5
          3.3.3.  APPORTIONMENT OF REVENUES. . . . . . . . . . . . . . . . .   5

4.  COLLABORATIVE RESEARCH AND DEVELOPMENT AND COMMERCIALIZATION PROGRAM--
    NON-CLINICAL MARKET. . . . . . . . . . . . . . . . . . . . . . . . . . .   6
    4.1.  RESEARCH AND DEVELOPMENT . . . . . . . . . . . . . . . . . . . . .   6
          4.1.1.  GOAL . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
          4.1.2.  RESEARCH SITES . . . . . . . . . . . . . . . . . . . . . .   6
    4.2.  THE COMMITMENT . . . . . . . . . . . . . . . . . . . . . . . . . .   6
          4.2.1.  RESEARCH MANAGEMENT COMMITTEE. . . . . . . . . . . . . . .   6
          4.2.2.  PRODUCT MANAGEMENT COMMITTEE . . . . . . . . . . . . . . .   6
          4.2.3.  HP COMMITMENTS . . . . . . . . . . . . . . . . . . . . . .   7
          4.2.4.  MTX COMMITMENTS. . . . . . . . . . . . . . . . . . . . . .   7
          4.2.5.  OTHER MTX SOFTWARE . . . . . . . . . . . . . . . . . . . .   7
    4.3.  TERM AND TERMINATION . . . . . . . . . . . . . . . . . . . . . . .   7
          4.3.1.  ORIGINAL TERM. . . . . . . . . . . . . . . . . . . . . . .   7
          4.3.2.  MATERIAL BREACH. . . . . . . . . . . . . . . . . . . . . .   8
          4.3.3.  TRANSFER OF OWNERSHIP BY MTX . . . . . . . . . . . . . . .   8
          4.3.4.  MTX DISSOLUTION. . . . . . . . . . . . . . . . . . . . . .   8
          4.3.5.  LIABILITIES AT TERMINATION . . . . . . . . . . . . . . . .   8
          4.3.6.  CONTINUED EXCLUSIVE RIGHT. . . . . . . . . . . . . . . . .   9
          4.3.7.  CONTINUED AGREEMENTS . . . . . . . . . . . . . . . . . . .   9
          4.3.8.  CESSATION OF SUPPLY. . . . . . . . . . . . . . . . . . . .   9
    4.4.  COLLABORATION INTELLECTUAL PROPERTY RIGHTS . . . . . . . . . . . .   9
          4.4.1.  HP INVENTIONS. . . . . . . . . . . . . . . . . . . . . . .   9
          4.4.2.  MTX INVENTIONS . . . . . . . . . . . . . . . . . . . . . .  10
          4.4.3.  JOINT INVENTIONS . . . . . . . . . . . . . . . . . . . . .  10
          4.4.4.  [Intentional Blank]  . . . . . . . . . . . . . . . . . . .  10
          4.4.5.  OWNERSHIP OF BACKGROUND AND OTHER INTELLECTUAL PROPERTY 
                  RIGHTS . . . . . . . . . . . . . . . . . . . . . . . . . .  10
          4.4.6.  MTX LICENSE OF BACKGROUND IPR TO HP. . . . . . . . . . . .  11
          4.4.7.  HP LICENSE OF BACKGROUND IPR TO MTX. . . . . . . . . . . .  11
          4.4.8.  PATENT PROSECUTION . . . . . . . . . . . . . . . . . . . .  11
          4.4.9.  CONFIDENTIAL INFORMATION . . . . . . . . . . . . . . . . .  13

5.  COMMERCIALIZATION PHASE. . . . . . . . . . . . . . . . . . . . . . . . .  15
    5.1.  COMMENCEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . .  15
    5.2.  RESPECTIVE MARKETS OF THE PARTIES. . . . . . . . . . . . . . . . .  15
          5.2.1.  BIOANALYTICAL MARKET . . . . . . . . . . . . . . . . . . .  15
          5.2.2.  BIOMEDICAL RESEARCH MARKET . . . . . . . . . . . . . . . .  17
          5.2.3.  DUAL NATURE ACCOUNTS . . . . . . . . . . . . . . . . . . .  18
          5.2.4.  GENOMICS . . . . . . . . . . . . . . . . . . . . . . . . .  18


                                        
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED


6.  REVENUES AND ROYALTIES . . . . . . . . . . . . . . . . . . . . . . . . .  19
    6.1.  HP SYSTEM. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  19
          6.1.1.  FORMULA SYSTEM PRICE . . . . . . . . . . . . . . . . . . .  19
          6.1.2.  HP SYSTEM ROYALTIES. . . . . . . . . . . . . . . . . . . .  19
    6.2.  COMPUTER HARDWARE AND PERIPHERALS. . . . . . . . . . . . . . . . .  20
    6.3.  CUSTOM APPLICATIONS SOFTWARE . . . . . . . . . . . . . . . . . . .  20
    6.4.  MTX AND HP CHIPS . . . . . . . . . . . . . . . . . . . . . . . . .  20
          6.4.1.  MTX SALES OF HP CHIPS. . . . . . . . . . . . . . . . . . .  20
          6.4.2.  MTX SALES OF MTX SPONSORED CHIPS . . . . . . . . . . . . .  20
          6.4.3.  HP SALES OF MTX SPONSORED CHIPS. . . . . . . . . . . . . .  20
          6.4.4.  HP SALES OF HP CHIPS . . . . . . . . . . . . . . . . . . .  20
    6.5.  MARKETING AND PROMOTION. . . . . . . . . . . . . . . . . . . . . .  21
    6.6.  PRESALES PRODUCT SUPPORT . . . . . . . . . . . . . . . . . . . . .  21
    6.7.  ROYALTY TERM . . . . . . . . . . . . . . . . . . . . . . . . . . .  21

7.  HP CHIPS AND [    *          ] CHIPS . . . . . . . . . . . . . . . . . .  21
    7.1.  COMMISSIONED HP CHIPS. . . . . . . . . . . . . . . . . . . . . . .  21
          7.1.1.  DEVELOPMENT PROGRAM. . . . . . . . . . . . . . . . . . . .  21
          7.1.2.  PRIORITY TO DEVELOPMENT. . . . . . . . . . . . . . . . . .  22
    7.2.  DEVELOPMENT AND SUPPLY AGREEMENT . . . . . . . . . . . . . . . . .  22
    7.3.  WARRANTIES AND LICENSES. . . . . . . . . . . . . . . . . . . . . .  22
          7.3.1.  PROPRIETARY GENETIC SEQUENCES. . . . . . . . . . . . . . .  22
          7.3.2.  LICENSE TO BACKGROUND IPR. . . . . . . . . . . . . . . . .  22
          7.3.3.  EXCLUSIVE RIGHTS TO HP CHIPS . . . . . . . . . . . . . . .  22
    7.4.  DUE DILIGENCE. . . . . . . . . . . . . . . . . . . . . . . . . . .  23
          7.4.1.  DEVELOPMENT OF HP CHIPS. . . . . . . . . . . . . . . . . .  23
          7.4.2.  GRANT OF LICENSE UPON BREACH . . . . . . . . . . . . . . .  23
    7.5.  REGULATORY FILINGS . . . . . . . . . . . . . . . . . . . . . . . .  23

8.  OPTION TO HP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  23
    8.1.  OPTION FEES. . . . . . . . . . . . . . . . . . . . . . . . . . . .  23
    8.2.  HP CLINICAL MARKET INSTRUMENT OPTION . . . . . . . . . . . . . . .  23
    8.3.  [          *          ] OPTION . . . . . . . . . . . . . . . . . .  24
    8.4.  EXERCISE OF PARTS OF OPTION. . . . . . . . . . . . . . . . . . . .  24
    8.5.  ROYALTY STRUCTURE AND LICENSING FEES . . . . . . . . . . . . . . .  24

9.  LICENSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  24

10.  COLLABORATION MONIES AND LICENSE FEE. . . . . . . . . . . . . . . . . .  24

11.  PAYMENTS APPLIED TO PURCHASE OF EQUITY POSITION . . . . . . . . . . . .  26

12.  PAYMENTS; BOOKS AND RECORDS . . . . . . . . . . . . . . . . . . . . . .  26
     12.1.  ROYALTY REPORTS AND PAYMENTS . . . . . . . . . . . . . . . . . .  26
     12.2.  PAYMENT METHOD . . . . . . . . . . . . . . . . . . . . . . . . .  26
     12.3.  CURRENCY CONVERSION. . . . . . . . . . . . . . . . . . . . . . .  26


                                        
<PAGE>

     12.4.  INSPECTION OF RECORDS. . . . . . . . . . . . . . . . . . . . . .  26
     12.5.  TAX MATTERS. . . . . . . . . . . . . . . . . . . . . . . . . . .  27

13.  REPRESENTATIONS AND WARRANTIES. . . . . . . . . . . . . . . . . . . . .  27
     13.1.  WARRANTIES . . . . . . . . . . . . . . . . . . . . . . . . . . .  27
     13.2.  REPRESENTATIONS. . . . . . . . . . . . . . . . . . . . . . . . .  27
     13.3.  MTX REPRESENTATION AND WARRANTY. . . . . . . . . . . . . . . . .  27
     13.4.  NON-ASSERTION AND ASSERTION OF CLAIMS BY THE PARTIES . . . . . .  28
            13.4.1.  NON-ASSERTION OF INFRINGEMENT CLAIMS. . . . . . . . . .  28
            13.4.2.  ASSERTION BY HP AFTER MATERIAL BREACH . . . . . . . . .  28
            13.4.3.  ASSERTION BY MTX AFTER MATERIAL BREACH. . . . . . . . .  28
     13.5.  RESIDUAL KNOWLEDGE OF EMPLOYEES AND FREEDOM TO RE-ASSIGN . . . .  28

14.  INDEMNIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . .  28
     14.1.  MTX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  28
     14.2.  HP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  29
     14.3.  PROCEDURE. . . . . . . . . . . . . . . . . . . . . . . . . . . .  29

15.  MISCELLANEOUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  29
     15.1.  GOVERNING LAWS . . . . . . . . . . . . . . . . . . . . . . . . .  29
     15.2.  WAIVER . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  29
     15.3.  ASSIGNMENT . . . . . . . . . . . . . . . . . . . . . . . . . . .  29
     15.4.  INDEPENDENT CONTRACTORS. . . . . . . . . . . . . . . . . . . . .  29
     15.5.  COMPLIANCE WITH LAWS . . . . . . . . . . . . . . . . . . . . . .  30
     15.6.  NOTICES. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  30
     15.7.  SEVERABILITY . . . . . . . . . . . . . . . . . . . . . . . . . .  30
     15.8.  FORCE MAJEURE. . . . . . . . . . . . . . . . . . . . . . . . . .  30
     15.9.  COMPLETE AGREEMENT . . . . . . . . . . . . . . . . . . . . . . .  30
     15.10.  DISPUTE RESOLUTION. . . . . . . . . . . . . . . . . . . . . . .  31
     15.11.  HEADINGS. . . . . . . . . . . . . . . . . . . . . . . . . . . .  31
     15.12.  SURVIVAL OF CLAUSES . . . . . . . . . . . . . . . . . . . . . .  31
     15.13.  COUNTERPARTS. . . . . . . . . . . . . . . . . . . . . . . . . .  31


                                        
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

                             COLLABORATION AGREEMENT

     THIS AGREEMENT, having an effective date of November 11, 1994, is made by
and between Hewlett-Packard Company (including its Affiliates) (hereinafter
collectively "HP"), a California corporation with a principal place of business
at 3000 Hanover Street, Palo Alto, California 94304, and Affymetrix (hereinafter
"MTX"), a California corporation with a principal place of business at 3380
Central Expressway, Santa Clara, California 95051.

1.  BASIC PRINCIPLES OF THE COLLABORATION

1.1.  INTENT.  HP and MTX (collectively the "Parties") intend that the result of
this collaboration ("Collaboration") will be a type of Array Reader (as defined
herein in Section 2) for use with MTX GeneChip-TM- products, which is brought to
market more quickly than either acting alone could accomplish, with more
effective technology than either alone could produce in the shortened time frame
and, along with other components necessary for a complete system (including both
instrument and application software) priced competitively for the targeted
markets.

1.2.  MUTUALLY PROFITABLE.  Both Parties intend the Collaboration to be mutually
profitable, and, as far as is possible when dealing with technology in such a
rapidly emerging area, have crafted terms which are born of the intention that
both Parties share fairly in the profits.  Specifically, MTX grants HP the
right-of-first refusal during the Collaboration to exploit new advances in
reader technology developed by or available to MTX during the Collaboration.

1.3.  ADJUSTMENT.  Both Parties recognize, too, that to the extent the actual
market conditions materialize differently than anticipated, adjustments may be
agreed to from time to time in order that the intent of the Collaboration may be
fulfilled.

1.4.  PRE-EXISTING IP.  Both Parties recognize that each has rights to
pre-existing intellectual properties which may directly or indirectly contribute
to the HP System.  It is understood that in the process of reaching a
Collaboration Agreement, both Parties will reveal to each other relevant
Background IP under appropriate confidentiality and nondisclosure provisions,
irrespective of whether the Background IP is an issued patent, a pending patent
application, a trade secret, know-how or otherwise.

1.5.  NEW PRODUCTS AND NEW USES.  To the extent that the Collaboration may
produce (i) new gene discoveries and applications and (ii) products with new
uses, both Parties will work towards terms which foster mutual success and
equitable apportionment of revenue therefrom.  Nothing in this Agreement is
intended to prohibit either Party from pursuing opportunities outside this
Collaboration so long as the Party does so without breaching any of the terms of
this Agreement.


                                        
<PAGE>

1.6.  EXPERIENCES OF MTX.  MTX has experience in the making of MTX Chips by
photolithographic methods and other methods currently under development; MTX
will focus resources toward the design and manufacture of array chips based on
MTX Chip technology, along with application specific software.  MTX represents
that it has developed technology that may be useful in developing a reader
instrument for MTX Chips.

1.7.  EXPERIENCES OF HP.  HP has experience as an instrument manufacturer with a
broad technological base; HP will focus resources toward the design and
manufacture of a reader instrument system, including software, capable of
reading MTX Chips.

1.8.  HP MARKET.  HP will evaluate and directly market Products in the "applied"
or Bioanalytical Market worldwide.

1.9.  MTX MARKET.  MTX will evaluate and directly market Products in the
"research" or Biomedical Research Market worldwide.

1.10.  EFFORTS.  Both Parties will use commercially feasible efforts to sell the
Products in their respective markets.

1.11.  FUNDING.  Within the scope of the Collaboration, MTX will fully fund, or
arrange to fund, development of MTX Chips and, to the extent MTX may legally do
so, will give HP sufficient notice of the nature of the intended product so that
marketing of Products can be effective; HP will fully fund development of the HP
System performed at HP and will fund reasonable development performed by
employees assigned to such development, excluding chip-related costs, at MTX as
described in the Workplan.

1.12.  SUPPLY PRICE.  HP agrees to supply the HP System to MTX for sale into the
Biomedical Research and clinical markets at the Formula System Price described
below.

2.  DEFINITIONS

2.1.  "AFFILIATE" shall mean collectively, all persons directly or indirectly
controlling, controlled by or under common control of a Party.  The term
"control" means the ownership, directly or indirectly, of at least fifty percent
(50%) of the voting stock of the controlled company in the case of a corporation
and at least fifty percent (50%) of the interest in net profits in the case of
an entity other than a corporation.

2.2.  "ARRAY READER" shall mean a fluorescent-based reader which reads MTX
Chips.

2.3.  "BACKGROUND IPR" shall mean IPR existing prior to the commencement of the
Collaboration.


                                        2
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED


2.4.  "BETA MODEL" shall mean an HP System meeting the agreed functionality
specifications set forth in the Workplan but not fully documented.

2.5.  "[      *       ] CHIPS" shall mean MTX Chips that are commissioned by HP
pursuant to the [          *          ] Option.

2.6.  "DNA CHIP" shall mean a solid support where the support includes a
plurality of single or double stranded DNA, RNA, or analog materials (or
combinations thereof) synthesized photolithographically on a surface of the
support at spatial locations that are known or may be determined.

2.7.  "EMERGING COMPANIES" shall mean a company whose first proprietary product
has not yet been offered for sale on a commercial basis in its major market.

2.8.  "HP CHIP" shall mean an MTX Chip commissioned and sponsored by HP.

2.9.  "HP SOFTWARE" shall mean software HP generates, as described in the
Workplan, for running the HP System.

2.10.  "HP SYSTEM" shall mean the Array Reader as described by the
specifications in the Workplan, with an output of pixel intensity versus
position data and shall include HP Software which runs the HP System, but shall
exclude computers, which are required to run the HP System.  

2.11.  "INTELLECTUAL PROPERTY RIGHTS" ("IPR") shall mean rights to protected
Intellectual Properties ("IP"), which shall mean patents, copyrights,
trademarks, trade secrets and maskworks.  (IPR may be subject to limitations
and/or obligations in any license from a third party.) 

2.12.  "INVENTION" shall mean intellectual property amenable to patent
protection.

2.13.  "MATERIAL BREACH" shall mean failure to pay monies, whether license or
royalties, due within thirty (30) days of their due date and absent a reasonable
dispute about the amount therefor for which the dispute resolution mechanism has
been initiated as provided for herein; failure of either Party to exercise
reasonable diligence in the development of their respective areas of
responsibility (the HP System from HP and the MTX Chips, including HP Chips and
[      *      ] Chips, from MTX); and inability or unwillingness of a Party to
meet the production or delivery schedules of its development and supply
agreement.

2.14.  "MTX CHIP" shall mean a DNA Chip made by or for MTX using in whole or in
part MTX IPR.


                                        3
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

2.15.  "MTX SOFTWARE" shall mean MTX-generated software for transforming pixel
intensity versus position information into gene sequence(s) that a given MTX
Chip is designed to identify.

2.16.  "MTX SPONSORED CHIP" shall mean an MTX Chip developed by MTX
independently of HP sponsorship.

2.17.  "NECESSARY REAGENTS" shall mean reagents, including probes, proprietary
to MTX, required for the use of MTX Chips for the use or uses for which any
given MTX Chip is intended and designed.

2.18.  "NET SALES" shall mean the [                                            
                                                                               
                                  *                                            
                                                                               
                                                                               
                   ] provided that where the Products are supplied by a Party or
its respective Affiliate, licensee or sublicensee free of charge or sold at a
price below the price at which it normally sells the Products to third parties
on a stand-alone basis, the Products shall be [                                
                                                                               
                                                *                              
                                         ]  Any transfer of Products for
evaluation or internal use purposes is deemed to have a net sales amount of
zero.

2.19.  "PATENT APPLICATION" shall mean any U.S. application, continuation,
continuation-in-part, reissue, reexamination, division or patent term extension
application or any foreign equivalent of the foregoing.

2.20.  "PROSECUTE" shall mean, in the context of prosecuting pending patent
applications, taking necessary actions, including conducting oppositions and
interferences, to perfect the patent rights to an invention.

2.21.  "PRODUCTION MODEL" shall mean an HP System which is manufactured by
standard HP manufacturing procedures.

2.22.  "PRODUCTS" shall mean the HP System, HP Software, MTX Chips, MTX Software
and Necessary Reagents.

2.23.  "RESIDUAL KNOWLEDGE" shall mean all Collaboration information in
nontangible form which is gained and retained in the mind in the normal course
of work by those employees (i) performing under this Agreement and (ii) having
access to Collaboration information, whether confidential or not, that is in
tangible or intangible form and that is not a protected IP.


                                        4
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

2.24.  "TYPE OF CHIP" shall mean chips of a particular part number characterized
by a common set of specifications.

2.25.  "WORKPLAN" shall have the meaning described in Section 4.1.1.

3.  MARKET SEGMENT DEFINITIONS--NON-CLINICAL MARKET

3.1.  BIOANALYTICAL MARKET.  The Bioanalytical Market consists of [            
                                                                               
                    *                                                          
    ]  HP will take the lead in sales and marketing in the Bioanalytical Market.


3.2.  BIOMEDICAL RESEARCH MARKET.  The Biomedical Research Market consists of [
                                                                               
                                                                               
                                                                               
        *                                                                      
                                           ]  MTX will take the lead in sales
and marketing in the Biomedical Market.

3.3.  DUAL-NATURE ACCOUNTS.

3.3.1.  DEFINITION.  Certain accounts may be classified as being either in the
Bioanalytical Market or the Biomedical Research Market.  The Parties will
mutually agree on account assignment and commit to actively introduce and market
the Products.  HP will be assigned accounts where HP has an active base of
analytical and measurement instruments business and agrees to make a concrete
commitment to introduce and actively market Products.  MTX will be assigned
accounts where MTX's expertise in molecular biology and DNA sequencing will give
MTX the lead.  Where it is to their mutual advantage, the Parties may also agree
to co-market dual nature accounts.  Co-market herein shall include initiating
pre-market and post-introduction development activities.

3.3.2.  ESTABLISHING ACCOUNTS.  The Parties agree (i) within six months after
the effective date of the Collaboration Agreement, to establish lists of target
accounts; (ii) within six (6) months prior to the launch of the Production
Model, to assign sales representatives to those accounts; and (iii) to revise
such accounts and assignments immediately prior to the introduction of the
Production Model and from time-to-time thereafter as appropriate.  The Parties
agree to negotiate terms to provide incentives to their sales forces to develop
their respective customer bases.

3.3.3.  APPORTIONMENT OF REVENUES.  To the extent that the Collaboration may
produce products with new uses, both Parties will work towards terms which
foster success and 


                                        5
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED


equitable apportionment of revenue to reflect respective interests and
contributions of the Parties.

4.  COLLABORATIVE RESEARCH AND DEVELOPMENT AND COMMERCIALIZATION PROGRAM--
NON-CLINICAL MARKET

4.1.  RESEARCH AND DEVELOPMENT.

4.1.1.  GOAL.  The Research and Development Phase of Collaboration will have a
goal of developing an HP System capable of reading MTX Chips for both the
Bioanalytical and Biomedical Research Markets. As goals, a Beta Model is to be
completed by [    *      ] and a Production Model to follow by [      *        ]
under a comprehensive Workplan for the HP System developed by HP and MTX
technical teams (the "Workplan Committee") and attached as Exhibit A hereto.

4.1.2.  RESEARCH SITES.  All commercially feasible efforts will be made by both
Parties to meet the Beta Model and Production Model goals stated in the
Workplan.  Both HP and MTX will perform research to develop the HP System,
including research on chemistry (primarily at MTX) as well as on the reader
instrument system (primarily at HP); manufacture of the developed HP System will
be the responsibility of HP.
          
4.2.  THE COMMITMENT.

4.2.1.  RESEARCH MANAGEMENT COMMITTEE.  The Parties agree that the mechanism for
managing the research staff under the Workplan and approving expenditures during
execution of the Workplan shall be the review and approval of a Research
Management Committee (RMC).  The RMC shall be composed of an equal number of
members of both Parties'  technology staffs.  All actions of the RMC will be by
unanimous consent.  In the absence of unanimous consent on a matter, it shall be
forwarded to the senior management of both Parties for final resolution.

4.2.2.  PRODUCT MANAGEMENT COMMITTEE.  The Parties agree that the responsibility
for managing the product development staff under the Workplan and reviewing
progress, and that the mechanism for approving changes to the HP System product
specification and requesting specific product orientated research of the RMC
during execution of the Workplan shall be through a Product Management Committee
(PMC).  The PMC may recommend to senior management to toll any date in this
Agreement if it finds that any Party, through that Party's actions or inactions,
has caused unavoidable delays in the performance of the other Party.  The PMC
shall be composed of an equal number of members of both Parties' personnel.  All
actions of the PMC will be by unanimous consent.  In the absence of unanimous
consent on a matter, it shall be forwarded to the senior management of both
Parties for final resolution.


                                        6
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

4.2.3.  HP COMMITMENTS.  HP shall commit monies and other resources sufficient
to realize the development of the HP System as delineated in the Workplan.  HP
agrees to pay reasonable "burden cost" (fully loaded cost) for MTX employees
assigned to and performing services in the development of the HP System as
described in the Workplan.

4.2.4.  MTX COMMITMENTS.  MTX will commit research, development and
manufacturing resources at MTX necessary to achieve the program goals of
manufacturing a minimum number of specific MTX Chips in quantities previously
agreed to and with performance characteristics previously agreed to to meet
market demand for such Chips.  The majority of MTX personnel assigned to perform
services and research as defined in the Workplan shall have substantial MTX
experience.

4.2.5.  OTHER MTX SOFTWARE.

4.2.5.1.  OVERALL SYSTEM.    HP will take the lead for development and
implementation of the overall system software architecture and will be
responsible for all software for the HP System, including output of the pixel
fluorescence intensities versus position on a chip, with the exception that MTX
will specify and implement image processing and data analysis software,
including transformation of the pixel fluorescence intensities versus position
on a chip, to identify the chip-specific bases in the target nucleic acid. 
Funding for the MTX-developed image processing and data analysis module will
either be provided by HP, but in such case HP will have no rights to such work
other than those specified in this Section 4.2.5.1, or by MTX, in which case MTX
may charge a fee, not to exceed [         *                   ] (said fee will
include cost of API software if supplied by MTX) per HP System, and supply the
module to HP directly.  If funded by HP, HP shall have a royalty-free license to
reproduce, use, and sell such module for HP Systems.  The approach will be based
on the optimization of resources to implement the Workplan with a recommendation
made by the RMC and subject to approval of HP and MTX management.  

4.2.5.2.  SOFTWARE API.  Definition of specifications and plan for
implementation of a software API for experimental protocols will be determined
by the PMC during the initial stages of the Workplan.  A graphical user
interface (GUI) will be specified and developed jointly by HP and MTX.  

4.3.  TERM AND TERMINATION.

4.3.1.  ORIGINAL TERM.  This Agreement, if not terminated earlier for cause,
that is, for a Material Breach which remains uncured sixty (60) days after
written notice, shall remain in effect until the end of the fifth (5th) full
calendar year from the date of the commencement of the Collaboration (the
"Original Term") and shall be extended thereafter for consecutive three-(3-)year
terms, unless either Party shall, upon six (6) months' written notice prior to
the termination of the current term to the other Party, state that it does not
wish to extend this Agreement.  Notwithstanding the foregoing, 


                                        7
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

either Party may, after the Original Term, terminate this Agreement for any
reason upon six (6) months' prior written notice to the other Party.  In the
event this Agreement is not extended beyond the Original Term or is terminated
other than for an uncured Material Breach after an extension, all licenses
granted herein which have not already been so converted shall convert to non-
exclusive licenses with the same terms, rights and obligations; HP shall
continue to supply to MTX the HP Systems being supplied by HP to MTX at the time
of such termination of this Agreement and MTX shall continue to supply to HP the
MTX Chips being supplied by MTX to HP at the time of such termination of this
Agreement on terms consistent with those of the Collaboration or supply
agreements entered into by the Parties prior to such termination.

4.3.2.  MATERIAL BREACH.  Notwithstanding the foregoing, upon a Material Breach
under this Agreement by either Party, the non-breaching Party may terminate this
Agreement by sixty (60) days' prior written notice to the other Party; said
notice shall become effective at the end of such sixty-day (60 day) period,
unless the breaching Party shall remedy such Material Breach during such sixty-
day (60 day) period.  In such event, the breaching Party shall not be entitled
to any license under Section 4.3.1 and shall be obligated to continue to supply
MTX Chips, HP Chips and [          *        ] in accordance with the terms
hereof, if MTX is the breaching Party and HP Systems, in accordance with the
terms hereof, if HP is the breaching Party.  

4.3.3.  TRANSFER OF OWNERSHIP BY MTX.  Should majority ownership of MTX be
transferred to others than those presently holding ownership without the prior
written consent of HP, HP may at its option terminate this Agreement forthwith
by written notice to MTX within sixty (60) days of notice from MTX of any such
change of ownership.  MTX shall promptly give such notice of change of ownership
to HP. 

4.3.4.  MTX DISSOLUTION.  Should a liquidation or dissolution of MTX occur;
should MTX effect or attempt an unauthorized transfer or assignment of this
Agreement; should MTX become insolvent; should MTX make a voluntary or
involuntary general assignment of its assets for the benefit of creditors;
should any petition in bankruptcy be filed by or against MTX; should a  receiver
or trustee be appointed for all or any part of MTX's property, HP may at its
option terminate this Agreement forthwith by written notice to MTX within sixty
(60) days of HP's knowledge of such event.  

4.3.5.  LIABILITIES AT TERMINATION.  The termination of this Agreement shall not
relieve either Party of any liability from any obligations which have accrued
hereunder prior to such termination, including duties of confidentiality or, in
the case of a Party whose Material Breach is the cause of termination, duties to
supply Products under the terms of the Collaboration or under any supply
agreement consistent with the terms of the Collaboration or the HP Option
entered into by the Parties.


                                        8
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

4.3.6.  CONTINUED EXCLUSIVE RIGHT.  Notwithstanding any termination provision in
this Agreement, if termination is not the result of a Material Breach by HP, HP
shall, by virtue of the license fee paid upon commencement of the Collaboration
Agreement, remain in possession of the exclusive right to make or have made,
sell and use the HP System and to sell Products in the Bioanalytical Market and
to such dual accounts as the Parties assign to HP for the entire exclusive
period under this Agreement.   
          
4.3.7.  CONTINUED AGREEMENTS.  Termination of the Collaboration Agreement, other
than upon a Material Breach by HP, will not affect the term of any development
or supply agreement entered into by the Parties pursuant to the HP Option then
in force and affect, except as may be provided in such agreement itself.

4.3.8.  CESSATION OF SUPPLY.

4.3.8.1.  HP SYSTEMS.  If HP ceases to supply the HP System, and MTX has been
selling HP Systems exclusively and continuously to read MTX Chips for the most
recent two (2) years or from the date when HP Systems are first available,
whichever is shorter, (on a country-by-country basis) in the Biomedical Research
Market, HP agrees to negotiate in good faith with MTX for a license for each
such country at a reasonable royalty rate to MTX to make, have made, use and
sell the HP System and for a supply agreement to provide MTX with HP proprietary
components for the HP System at a reasonable price for a reasonably limited
period.  

4.3.8.2.  MTX CHIPS.  MTX hereby grants to HP, effective if MTX ceases to supply
MTX Chips and if HP has been selling such MTX Chips, including HP Chips,
continuously (on a country-by-country basis) in its markets, a license for each
such country at the existing royalty rates to make or have made and sell such
MTX Chips, including Necessary Reagents and HP Chips, [        *    ] Chips and
such other then available MTX Chips that are suitable by the types of accounts
HP is serving in its markets at the time MTX ceases to supply.  

4.3.8.3.  GRANT OF LICENSE.  In either case, the Party ceasing to supply its
Product agrees to transfer to the other Party, as part of its grant of a
license, all know-how and technical data necessary to manufacture such Product.

4.4.  COLLABORATION INTELLECTUAL PROPERTY RIGHTS.  The Collaboration is intended
to facilitate invention by both Parties.  IPR relating to the work performed
under and as described in the Workplan shall be treated as follows:

4.4.1.  HP INVENTIONS.  Inventions made solely by HP employees within the scope
of the Workplan and during the term of the Collaboration ("HP Inventions") are
the property of HP.  HP Inventions will be cross-licensed royalty-free, without
the right to sublicense others, to MTX.  In the case of HP Inventions which are
applicable to array readers, such license for such use is for internal non-
commercial use only.


                                        9
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

4.4.2.  MTX INVENTIONS.  Inventions made solely by MTX employees within the
scope of the Workplan and during the term of the Collaboration ("MTX
Inventions") are the property of MTX.  MTX hereby grants HP an irrevocable,
royalty-free license, with sublicensing rights, to all such MTX Inventions.  MTX
shall not commercialize or license others to commercialize in whole or in part
any such MTX Inventions that are applicable to Array Readers for such use in the
Bioanalytical and Biomedical Markets without the written permission of HP while
HP is meeting its obligations to supply Array Readers to MTX for those markets. 
If MTX commercializes such MTX Inventions outside the Bioanalytical Market or
Biomedical Market, MTX shall (i) promptly pay HP [ * ] of the funding HP has
provided for the research resulting in such MTX Invention ("Funding") and (ii)
thereafter pay HP a reasonable royalty on such commercialization until an
additional [          *            ] of the Funding has been paid to HP.  MTX
shall in no event pay more than [      *         ] of the Funding to HP for such
commercialization of such MTX Inventions.

4.4.3.  JOINT INVENTIONS.

4.4.3.1.  DEFINITIONS.  Inventions made jointly by employees of HP and MTX
within the scope of the Workplan and during the term of the Collaboration
("Joint Inventions") will be jointly owned.  Neither Party may sublicense a
Joint Invention without prior written permission of the other Party, which
permission shall not be unreasonably withheld.  Any Invention resulting from
work performed under this Collaboration not promptly and fully disclosed in
writing upon conception, but in any event not later than ten (10) days after a
written Invention Disclosure is prepared, to the other Party as a sole HP
Invention or MTX Invention, as the case may be, shall be deemed a Joint
Invention upon dispute between the Parties.

4.4.3.2.  CROSS-LICENSEES.  Notwithstanding the foregoing, no prior written
permission is required for licenses to cross-licensees of either Party existing
as of the effective date of this Agreement.  Each Party hereby warrants that
none of the companies listed for that Party in Exhibit B is an existing cross-
licensee of the Party as of the effective date of this Agreement.  HP represents
to the best of its knowledge that the licenses with the cross-licensees listed
in Exhibit D are not germane to the technology applicable to Array Readers.

4.4.4.  [Intentional Blank]  

4.4.5.  OWNERSHIP OF BACKGROUND AND OTHER INTELLECTUAL PROPERTY RIGHTS.  Nothing
in the Collaboration Agreement is intended to alter or affect the ownership of
the Background IPR of the Parties or IPR developed after the term of the
Collaboration or outside the scope of the Workplan.  Each Party agrees to
promptly notify the other Party if any Background IPR or other IPR must be
acquired for the Collaboration; or, alternatively, notify the other Party
promptly on discovery if, to its knowledge, payment or a license to Background
IPR is required under Background IPR to or from a third party.


                                       10
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

4.4.6.  MTX LICENSE OF BACKGROUND IPR TO HP.  MTX grants HP a royalty-free
license to MTX Background IPR to make, have made, use or sell the HP System to
read MTX Chips.  However, this license to MTX Background IPR specifically shall
not constitute a license to HP to manufacture MTX Chips.

4.4.7.  HP LICENSE OF BACKGROUND IPR TO MTX.  HP grants MTX a royalty-free
license to HP Background IPR to make, have made, use or sell MTX Chips,
including HP Chips and [      *      ] Chips, and Necessary Reagents for
operation with HP Systems during the period that such Products are available for
sale by HP ("Available Period") and during the [     *       ] of unavailability
for sale by HP immediately preceding such Available Period (the "Unavailable
Years") if the Unavailable Years are solely a result of an exclusive license
with a third party.

4.4.8.  PATENT PROSECUTION.

4.4.8.1.  BACKGROUND IPR.  Subject to the terms of any other agreements with
third parties relating to Background IPR, each Party shall, at its option and
expense, be responsible for  Patent Applications and patents relating to its
Background IPR.

4.4.8.2.  SOLELY-OWNED INVENTIONS.  The inventing Party shall, at its option and
expense, be responsible for Patent Applications and patents relating to
Inventions solely made by such Party.

4.4.8.3.  JOINT INVENTIONS.

4.4.8.3.1.  RESPONSIBILITY.  HP shall, at its option, be responsible to prepare,
file, Prosecute and maintain in such countries it deems appropriate, Patent
Applications and patents relating to Joint Inventions.  HP and MTX shall equally
share the cost of all such activities.  MTX at any time may decline to share
prospective costs by serving HP with  written notice to that effect.  In the
event MTX declines to share or, having shared, to continue to share the cost of
such activities in any country, MTX shall cease to be joint owner and shall
promptly assign to HP its joint ownership of such Joint Inventions and/or
patents issuing thereon to HP for such country, reserving for itself an
irrevocable, non-exclusive, royalty-free, license to all such patents, including
those issuing from any such Patent Application.  In the case of Joint Inventions
which are applicable to array readers, such license for such use shall be for
internal use only.

4.4.8.3.2.  DECLINING FURTHER PATENTING EFFORT.  In the event HP declines to
file or having filed fails to further prosecute or maintain any such Patent
Applications or patents in any countries and MTX remains a joint owner of the
invention in such Patent Applications or patents in such countries, HP shall so
inform MTX at least sixty (60) days before the next action or filing is
required, and MTX shall have the right at its sole expense to prepare, file,
prosecute and maintain such Patent Applications and patents in such countries it
deems appropriate.  HP shall promptly assign to MTX its joint ownership in such


                                       11
<PAGE>

countries of (i) any patents issuing from such Patent Applications prosecuted or
maintained by MTX and (ii) any such patents being maintained by MTX, reserving
for itself and its cross-licensees existing at the time of the Agreement an
irrevocable, non-exclusive, royalty-free license to all such patents, including
those issuing from such Patent Applications.  In the case of Joint Inventions
which are applicable for the manufacture of DNA Chips, such license for such
use, except for cross-licensees existing at the time of the Agreement, shall be
for internal use only.

4.4.8.3.3.  FULL OWNERSHIP WITH ASSIGNMENT.  After assignment by a Party of any
Joint Invention to the other Party, the other Party hereto shall have full
ownership rights to the assigned Joint Inventions and patents issuing thereon,
if any, including the right to sublicense without accounting to the first Party.
  
4.4.8.4.  PROSECUTION BY NON-OWNER OTHER PARTY.  In the event that HP or MTX, as
the case may be (the "Owner"), declines to file or, having filed, declines to
further Prosecute and maintain any solely-owned Patent Applications or patents
claiming inventions made during the Collaboration, the other Party shall have
the right to take such actions, at its own expense, in the name of the Owner in
any country, in which event the Owner shall provide, at the other Party's
request and expense, all reasonable assistance.  If the Owner declines or fails
to take any such actions, such Owner shall notify the other Party hereto at
least sixty (60) days prior to the date the next action or filing is due to be
taken with respect to the subject Patent Application or patent.  Owner shall
assign such patents or patents issuing from such Patent Applications to the
other Party, reserving for itself and, in the case of HP, its cross-licensees an
irrevocable, royalty-free license to make, have made, use or sell products or
use processes covered by such patents.

4.4.8.5.  COOPERATION.  Each Party shall keep the other Party reasonably
informed as to the status of patent matters relating to the Collaboration on
request, comment on any documents which will be filed in any patent office, and
provide to the other Party copies of any material documents that such Party
receives from a patent office, including notice of all interferences, reissues,
reexaminations, oppositions or requests for patent term extensions.  Each Party
shall cooperate with and reasonably assist the other Party in such activities,
each Party bearing its own expenses, upon the other Party's request.

4.4.8.6.  ENFORCEMENT AND DEFENSE.

4.4.8.6.1.  ENFORCEMENT.

4.4.8.6.1.1.  SOLELY OWNED IPR.  If any IPR solely-owned by a Party (the "Owning
Party") which is necessary for the manufacture, use or sale of a Product is
infringed or misappropriated by a third party in any country in which the other
Party has rights to market such Product, the Owning Party shall upon discovery
promptly notify the other Party thereof.  The Owning Party shall have the
initial right (but not the obligation) to enforce, or defend any declaratory
judgment action against, or settle with the consent, 


                                       12
<PAGE>

which shall not be unreasonably withheld, of the other Party any claims against
such IPR at its own expense.  If the Owning Party fails to initiate a suit or
negotiation to enforce such IPR against a commercially significant infringement
by the third party within one (1) year of a request by the other Party and
actively pursue such suit or negotiation thereafter, the other Party shall no
longer be responsible for any royalty payments due the Owning Party on such
Product in that country of infringement after the one (1) year period so long as
such commercially significant infringement remains unabated, and all such
royalty payments due shall be forgiven.  The other Party may, at its own
expense, initiate such suit in the name of the Owning Party.  The other Party
shall keep the Owning Party hereto reasonably informed of the progress of any
such claim, suit or proceeding.  The other Party initiating the suit shall be
entitled to any recovery received as a result of any such claim, suit or
proceeding.  The other Party shall resume royalty payments to the Party upon a
successful action against the third-party infringer such (i) that the third-
party infringer is either enjoined from using the IP or required to pay the
Party a comparable royalty on a license to the IP or (ii) that the commercially
significant infringement has ceased.

4.4.8.6.1.2.  JOINT INVENTION.  Notwithstanding Section 4.4.8.6.1.1. above, in
the event that any Joint Invention is infringed or misappropriated by a third
party, HP and MTX shall mutually agree upon whether, and, if so, how, to enforce
such Joint Invention or defend such Joint Invention in a declaratory judgment or
similar proceeding.

4.4.8.6.1.3.  INFRINGEMENT CLAIMS.

4.4.8.6.1.3.1.  If the manufacture, sale or use of any Product pursuant to this
Agreement results in any claim, suit or proceeding alleging patent infringement
against HP or MTX, such Party shall promptly notify the other Party hereto in
writing setting forth the facts of such claim in reasonable detail.  The Party
subject to such claim shall have the exclusive right to defend and control the
defense of any such claim, suit or proceeding, at its own expense, using counsel
of its own choice; provided, however, it shall not enter into any settlement
which admits or concedes that any IP solely owned by or licensed from the other
Party hereto is invalid or unenforceable without the prior written consent of
such other Party.  The Party subject to the claim shall keep the other Party
hereto reasonably informed of all material developments in connection with any
such claim, suit or proceeding.  If the claim is based on the practice or use of
IP of the other Party, the other Party, at its own expense, shall have the right
to join the Party in the defense of the claim, suit or proceeding.

4.4.8.6.1.3.2.  If an infringement claim is brought against MTX for its
manufacture of MTX Chips, and MTX is required to make license payments therefor,
such license payments shall be the sole responsibility of MTX.

4.4.9.  CONFIDENTIAL INFORMATION.  Except as expressly provided herein, the
Parties agree that, for the term of this Agreement and for five (5) years
thereafter, the receiving Party 


                                       13
<PAGE>

shall not disclose to any third party any information furnished to it in written
form or, if furnished orally, reduced within thirty (30) days to written form,
and marked and identified as confidential information or trade secret by the
disclosing Party hereto pursuant to this Agreement except to the extent that it
can be established by the receiving Party by competent proof that such
information:

     (a)  was already known to the receiving Party, other than under an
          obligation of confidentiality, at the time of disclosure;

     (b)  was generally available to the public or otherwise part of the public
          domain at the time of its disclosure to the receiving Party;

     (c)  became generally available to the public or otherwise part of the
          public domain after its disclosure and other than through any act or
          omission of the receiving Party in breach of this Agreement;

     (d)  was independently developed by the receiving Party as demonstrated by
          documented evidence prepared contemporaneously with such independent
          development; or

     (e)  was subsequently lawfully disclosed to the receiving Party by a person
          other than the other Party.

4.4.9.1.  RESIDUALS.  Notwithstanding the foregoing section, employees and
consultants of a Party who perform services under this Agreement and have access
to Collaboration information shall not be prohibited from using the Residual
Knowledge relating to their participation in the Collaboration in future work
performed on behalf of such Party.

4.4.9.2.  NONDISCLOSURE OF TERMS.  Each Party agrees not to disclose except as
required by law, such as, but not limited to, filings with the U.S. Securities
Exchange Commission, the terms of this Agreement to any third party, other than
to such Party's attorneys, advisors, consultants and others on a need-to-know
basis under circumstances that ensure the confidentiality thereof, without the
prior written consent of the other Party.  Notwithstanding the foregoing, the
Parties shall agree upon a press release to announce the execution of this
Agreement, together with a corresponding question and answer ("Q&A") outline for
use in responding to inquiries about the Agreement; thereafter MTX and HP may
each disclose to third parties the information contained in such press release
and Q&A without the need for further approval by the other.  In addition, either
Party or both may make public statements regarding the progress of the
Collaboration and development and commercialization of Products including
announcement of the achievement of milestones and fees with respect thereto,
following consultation with the other Party.  


                                       14
<PAGE>

4.4.9.3.  PUBLICATION.  The contents of any proposed publication or public
disclosure ("Publication") by an employee of or consultant to HP or MTX (the
"Disclosing Party") describing the scientific results of the Collaboration shall
be subject to the prior review of the RMC at least thirty (30) days prior to
submission for such Publication by the Disclosing Party.  The members of the
other Party in the RMC shall be responsible for forwarding the contents of such
Publication to their respective company (the "Receiving Party").  The Receiving
Party shall notify the Disclosing Party in writing within such thirty (30) day
period whether the Receiving Party desires a Patent Application be filed on any
Invention disclosed in such Publication.  In the event that the Receiving Party
desires a Patent Application be filed, the Disclosing Party shall withhold such
Publication until the earlier that (i) a Patent Application is filed thereon, or
(ii) the Parties determine after consultation that no patentable invention
exists, or (iii) sixty (60) days after receipt by the Disclosing Party of the
Receiving Party's written notice of the Receiving Party's desire that such
Patent Application be filed.  Further, if such Publication contains information
of the Receiving Party that is subject to confidentiality and nondisclosure
restrictions under Section 4.4.9 the Disclosing Party agrees to remove such
information from the proposed Publication.

5.  COMMERCIALIZATION PHASE

5.1.  COMMENCEMENT.  The Commercialization Phase will begin when the Products
are available for sale and installation to customers on a commercial, but not a
test-market, basis.  

5.2.  RESPECTIVE MARKETS OF THE PARTIES.  As noted above, HP will market
Products to the Bioanalytical Market and MTX to the Biomedical Research Market
and, subject to the HP Option, to the clinical diagnostic market.  Dual nature
accounts will be assigned to either HP or MTX or will be co-marketed.

5.2.1.  BIOANALYTICAL MARKET.

5.2.1.1.  PRODUCTS.  HP will market Products to the Bioanalytical Market.

5.2.1.2.  EARLY INFORMATION.  In order to allow HP to maximally penetrate the
Bioanalytical Market, MTX will provide HP information on the nature and
availability of MTX Chips, including third-party sponsored chips, as soon as the
commitment to develop or manufacture is made, whichever is earlier, or, in the
event that there are restrictions on the disclosure of information on third-
party sponsored MTX Chips, as soon as such restrictions terminate; provided that
such disclosure shall be subject to any obligation of confidentiality by MTX to
a third party, which obligation MTX will use commercially feasible efforts to
limit so as to permit MTX to supply such information under an obligation of
confidentiality to the third party.  MTX will use commercially feasible efforts
to ensure that all such third-party sponsored MTX Chips will be compatible with
and available for HP Systems.


                                       15
<PAGE>
                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

5.2.1.3.  HP PURCHASE OF CHIPS AND REAGENTS.  MTX will supply and HP will
purchase MTX Chips, including HP Chips, and Necessary Reagents exclusively from
MTX for use with the HP System at a formula price equal to [                  
           *                            ] for said chips and reagents, but not
less than [ * ].  If the MTX [        *                  ] is greater than [ * ]
per chip, then the formula price will be based on a linear pricing scale from [
                           *                                                  ].
Above the [ * ] price to HP, the price to HP will be [       *        ].  In
the event that HP should promote MTX Chips as reusable items and should set its
pricing accordingly, the Parties will renegotiate in good faith the transfer
pricing provision of MTX Chips to HP. 

 5.2.1.4.  ROLLING FORECASTS FOR MTX CHIPS.

5.2.1.4.1.  Within thirty (30) days after HP has provided MTX with a Beta Model,
HP will provide MTX with a list of MTX Chips by type of chip and quantity it
anticipates purchasing for the coming calendar year ("List").  Within thirty
(30) days of receipt of the List, MTX will then provide HP with a price/volume
schedule ("P/V Schedule") for the year.  HP, within thirty (30) days after
receipt of the P/V Schedule from MTX, will provide MTX with a committed forecast
of its anticipated purchases of MTX Chips for the following [       *          
     ].  Thereafter, at least three (3) months prior to each calendar year HP
will provide MTX with a List for such calendar year, and, within thirty (30)
days of receipt of the List, MTX will provide HP with a P/V Schedule for that
calendar year.  Further, at least thirty (30) days prior to each calendar
quarter, HP will provide MTX a rolling forecast for the [           *          
 ].  HP shall purchase at least [*] of the MTX Chips forecasted for [      
*          ], at least [*] for the next quarter and at least [*] for the [  *  
   ].
          
5.2.1.4.2.  If HP's firm orders for shipment in any quarter exceeds [ * ] of its
forecast for such quarter or [ * ] of the total of its orders for shipment 
during the preceding quarter, MTX shall not be obligated to supply such excess 
over [ * ].  Chips will be shipped FOB at place of manufacture if manufactured 
in the U.S. or at U.S. port of entry if manufactured abroad.  In no event will 
the prices charged to HP be more than the lowest price charged to any third 
party for a comparable chip for a comparable use. 

5.2.1.5.  SUPPORT.

5.2.1.5.1.  MTX will provide reasonable application support to HP, through
training or otherwise, for the initial Product introduction to customers in the
Bioanalytical Market as HP staffs up its sales efforts.  If this support
involves the formal training of HP personnel, such training shall be held in a
single convenient location and HP shall be responsible for the travel and living
expenses of HP personnel during such training.

5.2.1.5.2.  In addition, on-going support of HP customer support relating to
pre-categorized chemistry problems associated with Products will be the
responsibility of 


                                       16
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

MTX.  However, where the problem is "combinatorial," related to the combination
of the chemistry and the measurement system, then the application problem will
be the responsibility of both Parties.  

5.2.1.6.  SEEDING THE BIOANALYTICAL MARKET.  HP recognizes the benefit of
efforts by MTX to seed the Bioanalytical Market as a significant component of
HP's market development.  HP agrees to cooperate with MTX in these efforts prior
to the availability of the Production Model.

5.2.1.7.  EXCLUSIVITY.

5.2.1.7.1.  From the commencement of the Collaboration until [      *       ],
except as provided in Section 5.2.1.6, MTX will not sell or otherwise distribute
to or agree that any other party may sell or distribute to any other party, or
license any other party therefor, any Array Reader whatsoever into the
Bioanalytical Market without the prior written consent of HP.  

5.2.1.7.2.  HP will not sell or promote or permit any distributor to sell or
promote based on the capability of reading non-MTX Chips an Array Reader which
incorporates protected MTX IP without prior written permission from MTX.
  
5.2.2.  BIOMEDICAL RESEARCH MARKET.

5.2.2.1.  PRODUCTS.  MTX will market the Products to the Biomedical Research
Market.  HP shall supply and MTX shall purchase HP Systems and system components
for the Biomedical Research Market exclusively from HP at the Formula System
Price set forth in Section 6 below.

5.2.2.2.  LIMITATION AND REPLACEMENT OF NON-HP READERS.  From the date HP makes
the Production Model available to MTX, MTX will not accept new orders for or
otherwise place any Array Readers other than HP Systems in the Biomedical
Research Market until December 1, 2001.  MTX agrees to introduce or permit to be
introduced no more than [      *          ] non-HP Array Readers (the "Maximum
Number") manufactured by or for MTX into the Biomedical Research Market before [
    *        ].  If HP fails to make available the Production Model to MTX by [
  *         ], then the Maximum Number is waived.  MTX will market the HP System
exclusively in the Biomedical Research Market for a period beginning when the
Production Model is available and ending on December 1, 2001.  When the
Production Model becomes available and non-HP Array Readers have been ordered to
customers but are yet undelivered ("back orders"), MTX will use commercially
feasible efforts to cover such back orders of non-HP Array Readers with HP
Systems.  Further, once the Production Model is available, MTX agrees, at HP's
request, to use commercially feasible efforts to "swap-out" at least [      *  
       ] of the non-HP Array Readers introduced into the Biomedical Research
Market but not more than a total of [    *   ] Array Readers.  


                                       17
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

HP and MTX will share equally the cost of the "swap-out".  HP and MTX will work
together to offer customers the opportunity to "swap out."  If the Production
Model is not ready for commercial sale before January 1, 1998, MTX will have no
obligation to "swap out."  

5.2.2.3.  ELECTION TO TERMINATE EXCLUSIVITY.  After December 1, 1999, MTX may
elect to terminate the period of exclusivity before the entire period of
exclusivity has elapsed if MTX gives HP six (6) months written prior notice of
such election and gives a reasonable quid pro quo to which HP agrees.

5.2.2.4.  ROLLING FORECASTS FOR HP SYSTEMS.  Within thirty (30) days after HP
has provided MTX a Beta Model, MTX will provide HP an estimate of the number of
HP Systems it anticipates purchasing:  (i) additional Beta Models, if any, for
the coming HP [       *     ] and (ii) Production Models for the four [        
  *       ] thereafter.  Within thirty (30) days of receipt of this volume
estimate, HP will then provide MTX with a price/volume schedule ("P/V Schedule")
for this period.  MTX, within thirty (30) days of receipt of the P/V Schedule
from HP, will provide HP with a committed forecast of its anticipated purchases
of HP Systems for the following [         *                ].  Thereafter, at
least thirty (30) days prior to each [      *        ], MTX will provide HP a
rolling forecast for the [         *                         ].  MTX shall
purchase at least [*] of the HP Systems forecasted for the current quarter, at
least [*] for the next quarter and at least [*] for the last quarter.  
          
5.2.2.5.  SERVICE CONTRACTS.  Where MTX sells HP service contracts with the
initial sale of an HP System, HP will have the obligation to perform such
service contracts commensurate with its obligations and quality standards when
it directly sells or includes a service contract together with sale of an HP
System.  All paid service contracts will be subject to HP's acceptance, which
shall not be unreasonably withheld.  If HP determines not to accept contracts in
a particular geographic location, HP will make available at a reasonable fee to
MTX or its designee service training, service manuals and component parts
reasonably to permit MTX or its designee to provide required services in such
location.  

5.2.3.  DUAL NATURE ACCOUNTS.  Once a dual nature account has been assigned to
either HP or MTX, the terms of this Agreement shall be applied as if it were in
the Bioanalytical or Biomedical Research Market, respectively.

5.2.4.  GENOMICS.

5.2.4.1.  RIGHT TO ENTER INTO THIRD-PARTY COLLABORATIONS.  MTX reserves the
right to enter into collaborations with third parties for the development of MTX
technology (including, but not limited to, MTX Chips) for measuring the presence
and level of nucleic acid sequences or genes and applying MTX technology to
those companies' development projects.  


                                       18
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

5.2.4.2.  RIGHT TO DISTRIBUTE THIRD-PARTY MTX CHIPS.  MTX will use commercially
feasible efforts to secure rights to distribution of any such collaborator's MTX
Chips broadly in the Bioanalytical Market for HP as soon as MTX has the right to
sell such chips other than to the third-party collaborator.  HP acknowledges
that these MTX Chips may have a royalty obligation to the third party
collaborator as a result of such third party's funding of the MTX Chip
development and/or as compensation for rights to sell MTX Chips based on
proprietary gene sequence information.  Notwithstanding the foregoing,
commercial sale of MTX Chips to either the collaborator or other third parties
(other than to the collaborator for purposes of research and development) shall
remain subject to HP's rights hereunder in the Bioanalytical Market.  

6.  REVENUES AND ROYALTIES 

6.1.  HP SYSTEM.

6.1.1.  FORMULA SYSTEM PRICE.  HP pricing of HP System sales to MTX shall be
HP's [                                                                         
                                                                               
                                      *                                        
                                                                               
                                                           ] FOB at place of
manufacture if manufactured in the U.S. or at U.S. port of entry if manufactured
abroad.  In no event shall HP charge MTX for HP Systems at prices higher than
the lowest price charged to any third party for comparable HP Systems sold under
comparable terms and conditions.

6.1.2.  HP SYSTEM ROYALTIES.

6.1.2.1.  ROYALTY RATES.  If HP has incorporated protected MTX IP into the HP
System or any component thereof, the HP System that HP sells to customers other
than MTX shall be subject to royalties.  Royalties on the HP System, if any,
will be paid to MTX according to the following table and further conditional
that HP has sold at least [     *   ] in Net Sales of the HP System to customers
other than MTX: 

The greater of:

          (a)  $[ * ]; or

          (b)  [*] of Net Sales of the HP System if the Gross Margin is less
than [*] and [*] if the Gross Margin is greater than or equal to [*].  

6.1.2.2.  DEFINITIONS.  HP gross margin ("Gross Margin") on the HP Systems is
defined as [                            *                          ] using
generally accepted accounting principles.  Royalties shall be calculated as a
percentage of the Net Sales and shall be paid in accordance with Section 12.


                                       19
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

6.2.  COMPUTER HARDWARE AND PERIPHERALS.  MTX will purchase computer hardware
and peripherals for HP Systems directly from vendors, or, at MTX's option,
through HP's Bioscience Products at a price to be negotiated at that time.  No
price for computer hardware and peripherals is established in this Agreement. 
HP agrees to transfer available HP computers for HP Systems to MTX at HP's
Bioscience Products Group's internal cost, plus reasonable handling and shipping
costs, at MTX' discretion.

6.3.  CUSTOM APPLICATIONS SOFTWARE.  During the term of this Collaboration
Agreement, both HP and MTX may develop custom applications software for use with
the HP System.  Such applications software shall not be considered part of the
"HP System", "HP Software" or "MTX Software" as previously defined.  Such
applications software are special applications offered as options to end users
of the HP Systems.  Either Party shall sell such custom applications software it
produces to the other Party at list price at the time the order is placed less 
[     *          ].  

6.4.  MTX AND HP CHIPS.  

6.4.1.  MTX SALES OF HP CHIPS.  MTX shall pay HP a royalty of [      *         ]
of Net Sales of HP Chips MTX sells into the Biomedical Research Market or, if to
an assigned dual account, also into the Bioanalytical Market.  

6.4.2.  MTX SALES OF MTX SPONSORED CHIPS.  MTX shall pay HP a royalty of [   * 
       ] of Net Sales of MTX Sponsored Chips MTX sells into the Biomedical
Research Market or, if to an assigned dual account, into the Bioanalytical
Market until MTX sells [         *        ] HP Systems, and thereafter [    *  
     ] of the Net Sales of MTX Sponsored Chips MTX sells into the Biomedical
Research Market until MTX sells [             *      ] HP Systems, whereupon MTX
shall no longer be obligated to pay HP a royalty on MTX Sponsored Chips it sells
into the Biomedical Research Market; provided, however, that MTX shall pay HP a
royalty of at least [       *      ] of the Net Sales of MTX Sponsored Chips MTX
sells into the Biomedical Research Market until December 31, 2001.

6.4.3.  HP SALES OF MTX SPONSORED CHIPS.  HP shall pay MTX a royalty of [   *  
        ] of Net Sales of MTX Sponsored Chips HP sells into the Bioanalytical
Market or, if to an assigned dual account, also into the Biomedical Research
Market.

6.4.4.  HP SALES OF HP CHIPS.  HP shall pay MTX a royalty of [      *      ]
of Net Sales of HP Chips HP sells into the Bioanalytical Market.  For Net Sales
of any one type of HP Chip exceeding [              *                   ] in any
one year, HP shall pay MTX a royalty of [         *      ] of Net Sales in
excess of [           *                      ] of that type of HP Chip HP sells
into the Bioanalytical Market.  


                                       20
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

6.5.  MARKETING AND PROMOTION.  HP and MTX will fund their marketing and
promotion activities for new Products in their respective markets commensurate
with similar new product introductions by HP's Analytical Products Group.  These
activities typically include advertising, product literature, seminars, field
application specialists, and technical articles.  The Parties will work
cooperatively to develop applicable materials.  HP agrees that an "Affymetrix"
and/or "GeneChip-TM-" nonpeelable, descriptive label (in compliance with the
"Value Added Business Design Standards of HP", and consistent with HP product
design labeling standards and guidelines, but no less prominent than HP's
"IntelTM Inside" labels) supplied by MTX will be affixed to each HP System.  MTX
will provide adequate prior trademark clearances, at its own expense, on any
label it provides to HP for such use, and will indemnify and hold HP harmless
for any liability resulting from HP's use of such MTX-provided label.  All uses
of a Party's trademarks will be approved by the Party owning such trademarks
prior to such uses.

6.6.  PRESALES PRODUCT SUPPORT.  HP recognizes the benefit of involvement of
experienced MTX scientific and marketing personnel in the development and
execution of seminars, training and other market development activities for the
Bioanalytical Market.  HP intends to utilize such MTX resources and agrees to
reasonably compensate MTX for their involvement in such activities.

6.7.  ROYALTY TERM.  The royalty obligations under this Agreement shall remain
in force, on a country-by-country and Product-by-Product basis, until the
expiration date of the last patent containing a valid claim covering such
Product in such country.  Upon expiration of such period with respect to any
Product in any country as provided in this Section, the licensed Party shall
have a fully paid-up license to make, have made, use and sell such Product in
such country.  Notwithstanding the foregoing, if a Product shall not at any time
have been covered by a valid patent in a particular country, but shall be
covered by or developed utilizing a Party's protected IP, the royalty
obligations hereunder shall nevertheless remain in force in such country for a
period of five years from the first commercial sale on a Product-by-Product
basis in such country, unless such Product is produced and sold in such country
by a third party without any royalty obligations to the licensing Party, in
which case the licensed Party will have no further royalty obligations for such
Product in such country.

7.  HP CHIPS AND [        *    ] CHIPS

7.1.  COMMISSIONED HP CHIPS.

7.1.1.  DEVELOPMENT PROGRAM.  MTX agrees to develop and manufacture HP Chips
that (i) are identified and commissioned by HP and approved by MTX and (ii), if
HP exercises the [               *     ] Option, include [       *     ] Chips,
pursuant in each instance to a mutually agreed-to development program.  HP shall
bear the cost of development of such HP Chips as scheduled and agreed to in the
development program.  The payment of such development costs will be referred to
as "sponsorship," 


                                       21
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

i.e., HP, as payor of said costs, will be deemed to have "sponsored" such chips.
(Chips paid for by MTX or third parties collaborating with MTX will be deemed
"MTX Sponsored Chips").

7.1.2.  PRIORITY TO DEVELOPMENT.  In accordance with the preceding paragraph,
MTX shall enter, at HP's request, a chip development program and shall give
priority to the development for HP of up to a total of [  *   ] HP Chips,
including [        *    ] Chips if HP exercises the [          *          ]
Option, at any one time.   

7.2.  DEVELOPMENT AND SUPPLY AGREEMENT.  Upon the commissioning of an HP Chip,
including a [        *         ], MTX and HP will enter into a development and
supply agreement for such chip.

7.3.  WARRANTIES AND LICENSES.

7.3.1.  PROPRIETARY GENETIC SEQUENCES.  Upon the commissioning of an HP Chip
including a [       *     ] Chip, HP will warrant and represent to MTX that it
owns or controls the proprietary gene sequences necessary to make, use and sell
any such HP Chip.  Further HP will cross-license MTX to make, use and sell each
such HP Chip during the term of this Agreement for the Biomedical Market,
subject to any restrictions agreed upon in the development and supply agreement
negotiated upon commissioning said HP Chip.

7.3.2.  LICENSE TO BACKGROUND IPR.  Nothing in the Collaboration is intended to
alter ownership of Background IPR.  MTX grants a license to HP for any MTX
Background IPR for making, using or selling the HP System to read MTX Chips.  HP
grants a license to MTX for any HP Background IPR to make, use or sell HP Chips,
including [       *     ] Chips, and Necessary Reagents during the period when
such Products are available for sale by HP.  Except as to the aforementioned
grants, no other rights in protected Background IPR are deemed to be granted
through the Collaboration Agreement.  However, both parties agree to negotiate
in good faith for rights to use a Party's protected Background IPR where and to
the extent necessary to practice inventions of the other Party arising out of
the Workplan and necessary to commercialize HP Systems by HP and MTX Chips by
MTX.

7.3.3.  EXCLUSIVE RIGHTS TO HP CHIPS.  All rights in HP Chips shall be exclusive
to HP in the Bioanalytical Market for no less than [     *       ] from first
commercial sale, or such longer period provided by MTX to any third party in the
first major agreement entered into by MTX with such third party for development
by MTX on behalf of such third party of functionally specific MTX Chips.


                                       22
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

7.4.  DUE DILIGENCE.

7.4.1.  DEVELOPMENT OF HP CHIPS.  MTX shall use commercially feasible efforts to
conduct as expeditiously as practicable the development of HP Chips, including 
[       *     ] Chips if HP exercises the [       *             ] Option.  MTX
will fairly allocate resources reasonably necessary to develop HP Chips,
including [       *     ] Chips, and supply them to HP.

7.4.2.  GRANT OF LICENSE UPON BREACH.  In the event MTX does not meet its due
diligence obligations in developing a commissioned HP Chip, including a [      
*     ] Chip, and after sixty (60) days of notice from HP is unable or unwilling
to cure such default, MTX hereby grants HP a license at reasonable royalty rates
to make or have made such HP Chip immediately effective upon such event.  Such
license from MTX to HP shall be at existing royalty rates to make or have made
such chip.

7.5.  REGULATORY FILINGS.  HP shall diligently pursue necessary regulatory
filings to market [        *     ] Chips and HP System on a country-by-country
basis.  If HP rights with respect to any [       *     ]  Chips and HP System
shall terminate because of a Material Breach by HP, HP shall promptly provide
MTX with access to regulatory filings, if any, made by HP with respect to such 
[       *     ] Chip and HP System together with the underlying preclinical and
clinical data, with respect to such [       *     ] Chip and HP System, and
cooperate with MTX, at MTX's expense, in obtaining all regulatory approvals
necessary to market such [       *     ] Chip and HP System.  MTX may use and
incorporate such filings and data in support of applications for approval of
such HP System and [       *     ] Chip worldwide at its own risk.  MTX will
indemnify and hold HP harmless from any liability resulting from its use of any
such filings and data.

8.  OPTION TO HP

8.1.  OPTION FEES.  MTX grants HP a one (1) year option, renewable for two (2)
consecutive one (1) year periods, for a total of three (3) years ("HP Option")
upon payment of an annual fee of [               *                     ] by HP. 
The HP Option has two parts, each of which may be exercised independently of, or
in conjunction with, the other.  At the end of the third anniversary of the HP
Option, the HP Option may be renewed for two (2) additional one (1) year
periods, with Part 2 converting to a right-of-first opportunity, to be exercised
within a sixty-day (60-day) period after notice, to the same exclusive license,
upon payment of an annual fee of [           *                   ] by HP.

8.2.  HP CLINICAL MARKET INSTRUMENT OPTION.  Part 1 of the HP Option ("HP
Clinical Market Instrument Option") gives HP the non-exclusive right to sell,
distribute or otherwise dispose of the HP System into the hospital clinical
market (the "HP Clinical 


                                       23
<PAGE>

                                  CONFIDENTIAL
                                    TREATMENT
                                    REQUESTED

Market") and such other segments of the clinical diagnostic market as the
Parties in their discretion may agree.

8.3.  [          *          ] OPTION.  Part 2 of the HP Option ([        *     
      ] Option") gives HP the right to commission the development by MTX of [ 
   *     ] Chips using gene sequences available to HP for use by  [       *   
                    *                                                         ]
and an exclusive right to market and sell each [         *   ] Chip in the HP
Clinical Market for no less than three (3) years from first commercial sale of
such [       *     ] Chip, or such longer period provided by MTX to any third
party for development by MTX on behalf of such third party of functionally
specific MTX Chips.  
      
8.4.  EXERCISE OF PARTS OF OPTION.  Each of the two parts of the HP Option is
deemed to be equal in value and cost.  Any part of the HP Option may be
exercised in conjunction with or independently of any other part of the option. 
The HP Option, or either part of the HP Option, is deemed to be exercised when a
writing to that effect has been sent to the MTX representative identified in
Section 15.6 for the receipt of notice.  After the HP Option, or either part
thereof, has been exercised, a development and supply agreement shall be
negotiated in good faith by the Parties.

8.5.  ROYALTY STRUCTURE AND LICENSING FEES.  The royalty structure for HP sales
in the HP Clinical Market shall be the same as that adopted by the Parties for
the non-clinical market (see Section 6 above).  The licensing fees for
exclusivity shall not exceed [             *                       ] for each
year during the period prior to regulatory approval of the Products of such HP
sales and during the period of exclusivity, which commences upon regulatory
approval of such Products.  HP will use due diligence to pursue market
opportunities pursuant to the license received upon exercise of the HP Option.
After the period of exclusivity ends, no licensing fee apart from per chip
royalty on MTX Chips sold by HP shall be due MTX from HP.

9.  LICENSES 

When any exclusive license granted under this Agreement expires or terminates
other than for an uncured Material Breach, such license shall automatically
convert to a non-exclusive license under the same terms and conditions as the
expired or terminated exclusive license and shall be revocable only upon an
uncured Material Breach.

10.  COLLABORATION MONIES AND LICENSE FEE

The Collaboration depends on a commitment of resources on the part of both
Parties.  These commitments have been set forth in greater detail above.  In
recognition of the need of MTX to have capital early in the commercialization
stage, HP agrees to pay monies to MTX under the Collaboration Agreement for
licenses described hereinabove as follows:


                                       24
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

     $[   *   ]     paid within fifteen (15) days after the signing of this
                    Agreement, as a nonrefundable consideration for an
                    irrevocable five (5) year exclusive license and access to
                    MTX Background IP.  

     $[  *  ]       first milestone payment payable when the PMC deems that the
                    first milestone, as defined and interpreted by the PMC, has
                    been met, but in no case later than [       *              
                       ] after the signing of this Agreement.  

     $[  *  ]       second milestone payment payable no later than [       *  
                     ], tied to delivery to MTX of a Beta Model of the HP
                    System.  This payment is reduced to $[  *  ] if HP delivers
                    [   *   ] Beta Models to MTX by [     *     ], and is
                    eliminated in its entirety if HP delivers Production Models
                    to MTX by [     *       ].

     $[  *  ]       third milestone payment payable upon demonstrated capacity
                    of MTX to manufacture MTX Chips in sufficient quantity to
                    satisfy the minimum order level for HP's first annual
                    forecasted volume.

     $[  *  ]       initial prepayment for HP sponsorship of HP Chips (pre-assay
                    and assay optimization, where HP is billed by MTX at
                    fully-loaded costs), of which $[  *  ] is payable within
                    thirty (30) days of execution of this Agreement and $[  * ]
                    is payable within 135 days of execution of this Agreement.

     $[  * ]        $[  * ] for each of the first [    *  ] years of the HP
                    Option, payable within fifteen (15) days after the signing
                    of this Agreement and at each of the next two anniversaries
                    thereof thereafter.

     $[  * ]        $[  * ] for each of the last [  *  ] years of the HP Option,
                    in which Part 2 is a right-of-first-opportunity, payable on
                    the third and fourth anniversary dates of the signing of
                    this Agreement.

In addition to the collaboration and license fee payments described above, HP
agrees to pay reasonable "fully-loaded" cost for MTX employees assigned to the
development of the HP System, or assigned to collaborative research on Chemical
Issues and Hybridization towards possible future generation readers, as
described in the Workplan and for such duration as the RMC has deemed necessary,
but in no event less than two (2) years.

MTX will bill HP monthly for "fully-loaded" costs for MTX employees performing
services in development of the HP System, including payroll, taxes and benefits,
laboratory and supplies expenses, and reasonable occupancy and other overhead
charges.  In no case shall the charge to HP for assigned MTX people exceed an
annualized charge 


                                       25
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                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

of $[  *  ] per person.  If HP should dispute the reasonableness of these
charges, the appropriate management committee will either resolve by unanimous
agreement or recommend a negotiated resolution to HP and MTX senior management.

11.  PAYMENTS APPLIED TO PURCHASE OF EQUITY POSITION

If HP purchases an equity position in MTX from MTX within twenty-four (24)
months of the effective date of this Agreement, MTX agrees to apply the $[ * ] 
license fee paid pursuant to Section 10 toward the purchase of any such
equity.  Notwithstanding the foregoing, HP has no obligation to purchase, and
MTX has no obligation to sell, MTX capital stock hereunder.

12.  PAYMENTS; BOOKS AND RECORDS

12.1.  ROYALTY REPORTS AND PAYMENTS.  After the first commercial sale of a
Product on which royalties are required, HP or MTX, as the case may be, shall
make semi-annual written reports to the other Party within sixty (60) days after
the end of each reporting period, stating in each such report the aggregate Net
Sales of each Product sold during the period upon which a royalty is payable
under Section 6 above.  Concurrently with the making of such reports each Party
shall pay to the other Party royalties at the rates specified in Section 6
above.  HP's reporting period for the purpose of this section shall be each HP
fiscal half year, or the six (6) month period ending each April 30th and October
31st.

12.2.  PAYMENT METHOD.  All payments due under this Agreement shall be made by
bank wire transfer in immediately available funds to an account designated by
MTX or HP, as the case may be.  All payments hereunder shall be made in U.S.
Dollars.  Any payment more than thirty (30) days late shall bear interest to the
extent permitted by applicable law at the prime rate as reported by the Chase
Manhattan Bank.  New York, New York, on the date such payment is due, plus an
additional [      *       ] calculated on the number of days such payments is
delinquent.  This Section 12.2 shall in no way limit any other remedies that a
Party may have.  

12.3.  CURRENCY CONVERSION.  If any currency conversion shall be required in
connection with the calculation of royalties hereunder, such conversion shall be
made using the selling exchange rate for conversion of the foreign currency into
U.S. Dollars, quoted for current transactions reported in the Western U.S.
edition of THE WALL STREET JOURNAL for the last business day of the reporting
period to which such payment pertains.

12.4.  INSPECTION OF RECORDS.  HP and MTX shall keep complete and accurate books
of account and records for the purpose of determining the royalty amounts
payable under this Agreement.  Such books and records shall be kept at the
principal place of business of such Party, as the case may be, for at least
three (3) years following the end of the reporting period to which they pertain.
Such records will be open for inspection during 


                                       26
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

such three-year (3-year) period by a representative or agent of MTX or HP for
the purpose of verifying royalty statements hereunder.  Such inspections may be
made no more than once each calendar year, at reasonable times and on reasonable
notice.  Inspections conducted under this Section 12.4 shall be at the expense
of the inspecting Party, unless a variation of error producing an increase
exceeding [     *         ] of the amount stated for any period covered by the
inspection is established in the course of any such inspection, whereupon all
costs relating to the inspection for such period and any unpaid amounts that are
discovered will be paid promptly by the Party being inspected.
     
12.5.  TAX MATTERS.  Each Party receiving royalty payments shall be solely
responsible for any assessment of taxes thereon.  If a Party has made payment of
taxes to a governmental agency on behalf of the other Party and has deducted
such payment from the royalties due the other Party, the Party shall provide
supporting documentation evidencing such tax payment made with its royalty
payment. 

13.  REPRESENTATIONS AND WARRANTIES

13.1.  WARRANTIES.  Each party warrants and represents to the other that it has
the legal rights and power to extend the rights granted herein to the other in
this Agreement, that each has the full right to enter into this Agreement and to
fully perform its obligations hereunder, and that neither has made nor will make
any commitments to third parties in conflict with or in derogation of such
rights or this Agreement.

13.2.  REPRESENTATIONS.  As of the effective date of this Collaboration, HP, to
the best of its knowledge, does not own or control any issued patents or Patent
Application which would act to preclude MTX from making or supplying MTX Chips. 
This representation is based on and limited by the fact that the commercial form
of MTX Chips is not presently known and it is not possible at this time for HP
to know completely its pending Patent Applications and issued patents.

13.3.  MTX REPRESENTATION AND WARRANTY.  MTX represents and warrants that, as of
the effective date of this Agreement:

     (i)   it has made accessible for review to HP all material documentations
           relevant to all MTX IPR relating to the Array Reader and the 
           chemistry and hybridization research under the Workplan, including 
           the patents and Patent Applications in Exhibit C, which are all the 
           relevant MTX Inventions relating to the HP System; 

     (ii)  to its knowledge, no third party is infringing any such IPR, and 
           MTX's use of such IPR is not infringing or violating, and has not 
           been alleged to infringe or violate, the IPR of any third party;


                                       27
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

     (iii) to its knowledge, no proceedings have been instituted or are
           pending that challenge the validity of the IPR; and

     (iv)  it has fully disclosed to HP any third-party patent rights or other
           proprietary rights that, to its knowledge, might yield a claim 
           against MTX, or those claiming by, through or under MTX (including HP
           under this Agreement) for use of such patent and proprietary rights, 
           and such full disclosure includes but is not limited to all legal 
           opinions MTX has obtained on such third-party rights.

13.4.  NON-ASSERTION AND ASSERTION OF CLAIMS BY THE PARTIES.

13.4.1.  NON-ASSERTION OF INFRINGEMENT CLAIMS.  HP and MTX agree that neither
Party will assert against the other Party, or its vendees, mediate or immediate,
any claims for patent infringement based on the manufacture, use or sale of MTX
Chips by MTX and HP Systems by HP.  This agreement of non-assertion shall apply,
however, only to patents and to claims of patents which are directed
specifically to such Products and only for the term of the Collaboration
Agreement or while the licenses granted herein to the respective Parties are in
effect.
          
13.4.2.  ASSERTION BY HP AFTER MATERIAL BREACH.  If HP terminates the
Collaboration because of a Material Breach by MTX, HP is not precluded from
asserting a patent claim after the termination of the Collaboration.

13.4.3.  ASSERTION BY MTX AFTER MATERIAL BREACH.  If MTX terminates the
Collaboration because of a Material Breach by HP, HP shall not assert a claim
against any patent identified in Exhibit C and issued to MTX prior to such
termination.

13.5.  RESIDUAL KNOWLEDGE OF EMPLOYEES AND FREEDOM TO RE-ASSIGN.  It is
understood and agreed between the Parties (i) that both Parties have the right
to assign and reassign employees and to use employees as the employer Party, in
its sole discretion, deems appropriate and (ii) that such employees may use
Residual Knowledge in the performance of services for the employer Party as set
forth in this Agreement.  

14.  INDEMNIFICATION

14.1.  MTX.  [                                                              
                                                                            
                                                                            
                                                                            
                                                                            
                                *                                           
                                                                            
                                                                            
                                                 ]

                                       28
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

[                                        *                                  
                     ]
14.2.  HP.  [                                                               
                                                                            
                                                                            
                                                                            
                                      *                                     
                                                                            
                                                                            
                                                                             
                                                                            
                                                                         ].

14.3.  PROCEDURE.  In the event that either Party intends to claim
indemnification (the "Indemnitee") under this Section 14, the Party shall
promptly notify the other Party in writing of such Liability.  The indemnifying
Party shall have the right to control the defense thereof with counsel mutually
satisfactory to the Parties; provided, however, that any Indemnitee shall have
the right to retain its own counsel, with the fees and expenses to be paid by
the indemnifying Party, if representation of any Indemnitee by the counsel
retained by the indemnifying Party would be inappropriate due to actual or
potential differing interests between such Indemnitee and the other Party
represented by such counsel in such proceeding.  The Indemnitee shall cooperate
with the indemnifying Party and its legal representatives in the investigation
of any action, claim or liability covered by this Section 14.

15.  MISCELLANEOUS

15.1.  GOVERNING LAWS.  This Agreement and any dispute arising from the
performance or breach hereof shall be governed by and construed and enforced in
accordance with, the laws of the state of California, without reference to
conflicts of laws principles.

15.2.  WAIVER.  It is agreed that no waiver by any Party hereto of any breach of
default of any of the covenants or agreements herein set forth shall be deemed a
waiver as to any subsequent and/or similar breach or default.

15.3.  ASSIGNMENT.  This Agreement shall not be assignable by either Party to
any third party hereto without the written consent of the other Party herein;
except either Party may assign this Agreement, without such consent, to an
entity that acquires substantially all of the business or assets of such Party
to which this Agreement pertains, whether by merger, reorganization,
acquisition, sale, or otherwise.

15.4.  INDEPENDENT CONTRACTORS.  The relationship of the Parties hereto is that
of independent contractors.  Each Party hereto is not deemed to be an agent,
partner or 


                                       29
<PAGE>

joint venturer of the other Party for any purpose as a result of this Agreement
or the transactions contemplated thereby.

15.5.  COMPLIANCE WITH LAWS.  In exercising its rights under this Agreement,
each Party shall fully comply with the requirements of any and all applicable
laws, regulations, rules and orders of any governmental body having jurisdiction
over the exercise of rights under this Agreement.

15.6.  NOTICES.  All notices, requests and other communications hereunder by a
Party shall be in writing and shall be personally delivered or sent by telecopy
or other electronic facsimile transmission or by registered or certified mail,
return receipt requested, postage prepaid, in each case to the respective
address specified below, or such other address as may be specified in writing to
the other Party hereto:

               MTX: _____________________________
                    President, Affymetrix
                    3380 Central Expressway
                    Santa Clara, California 95051

HP:_____________________________       ____________________________________
   James W. Serum, Ph.D.              Stephen P. Fox, Associate General Counsel
   Gen Manager - BioScience Products  Director, Intellectual Property
   HP Corporate Legal                 HP Corporate Legal
   3000 Hanover Street                3000 Hanover Street      
   Palo Alto, California 94304-1185   Palo Alto, California 94304-1185

15.7.  SEVERABILITY.  In the event that any nonmaterial provision of this
Agreement becomes or is declared by a court of competent jurisdiction to be
illegal, unenforceable or void, this Agreement shall continue in full force and
effect without said provision.

15.8.  FORCE MAJEURE.  Nonperformance of either Party (except for payment
obligations) shall be excused to the extent that performance is rendered
impossible by strike, fire, earthquake, flood, governmental acts or orders of
restrictions, failure of suppliers, or any other reason where failure to perform
is beyond the reasonable control and not caused by the negligence, intentional
conduct or misconduct of the nonperforming Party.

15.9.  COMPLETE AGREEMENT.  This Agreement with its Exhibits constitutes the
entire agreement, both written and oral, between the Parties with respect to the
subject matter hereof, and that all prior agreements respecting the subject
matter hereof, either written or oral, expressed or implied, shall be null and
void.  No amendment hereto shall be effective unless it is reduced and agreed to
writing and executed by the respective duly authorized representatives of HP and
MTX.


                                       30
<PAGE>

15.10.  DISPUTE RESOLUTION.  Any dispute arising from or under this Agreement
which is not settled by mutual consent shall be finally settled by binding
arbitration, conducted in accordance with the Commercial Arbitration Rules of
the American Arbitration Association by three (3) arbitrators appointed in
accordance with said rules.  The arbitration shall be held in Palo Alto,
California.  In the event of any dispute arising regarding the achievement of
the milestones in Section 10 above, the arbitrators shall be independent experts
in pharmaceutical and diagnostic product development (including clinical
development and regulatory affairs) in the U.S.  The costs of the arbitration,
including administrative and arbitrators' fees, shall be shared equally by the
parties.  Each Party shall bear its own costs and attorneys' and witness fees. 
A disputed performance or suspended performances pending the resolution of the
arbitration must be completed within thirty (30) days following the final
decision of the arbitrators or such other reasonable period as the arbitrators
may determine in a written opinion.  Any arbitration subject to this
Section 15.10 shall be completed within one (1) year from the filing of notice
of a request for such arbitration.

15.11.  HEADINGS.  The captions to the several sections hereof are not a part of
this Agreement, but are included merely for convenience of reference only and
shall not affect its meaning or interpretation.

15.12.  SURVIVAL OF CLAUSES.  The following sections (including their
subsections) of this Agreement shall survive any termination of the agreement: 
4.3.5-4.3.8, 4.4, 6, 7.5, 9, 12, 13, 14, 15.1, 15.2, 15.4, 15.10 and 15.12.

15.13.  COUNTERPARTS.  This Agreement may be executed in counterparts, each of
which shall be deemed to be an original and both together shall be deemed to be
one and the same agreement.

     IN WITNESS WHEREOF, the Parties hereto have caused this Agreement to be
duly executed by their authorized representatives and delivered in duplicate
originals as of the effective date.

HEWLETT-PACKARD COMPANY  AFFYMETRIX, INC.

<TABLE>
<S>                          <C>              <C>                       <C>
By: /s/ Douglas K. Carnahan  Dated: 11/11/94  By: /s/ David B. Singer   Dated: 11/11/94
    -----------------------         --------      -------------------          -------
Douglas K. Carnahan                               David B. Singer              
Vice President and                                President and Chief     
General Manager                                   Executive Officer  
Measurement Systems Organization
                                            By: /s/ Stephen P.A. Fodor  Dated: 11 Nov 94
                                                ----------------------         ---------
                                                Stephen P.A. Fodor
                                                President and Chief             
                                                Technical Officer
</TABLE>

                                       31
<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

                                    EXHIBIT A
              WORKPLAN FOR AFFYMETRIX/HEWLETT-PACKARD COLLABORATION
              FOR RESEARCH AND DEVELOPMENT OF GENECHIP-TM- READERS


CONTEXT

This Workplan describes the technical research and product development
objectives, plans, and organization for the collaboration between Affymetrix
("MTX") and Hewlett-Packard ("HP").  It is set in the context of being Exhibit A
of the MTX-HP Collaboration Agreement which describes the business and marketing
aspects of the collaboration.

If any provision of this Workplan conflicts with the terms and conditions of the
Collaboration Agreement, the terms and conditions of the Collaboration Agreement
shall control.  Capitalized terms used but not defined herein have the meanings
specified in Section 2 of the Collaboration Agreement.

OBJECTIVES

To describe the development of a high performance nucleic acid chip reader
system (The HP System)  as required by the planned evolution of MTX GeneChip 
technology and an understanding of customer requirements.  A working
specification appears later in this document.  

To describe collaborative research with the objective of establishing a
technology base for use in the initial product offering if results are available
in a timely fashion, and for use in possible subsequent generations of the HP
System.

PRODUCTS: THE HP SYSTEM

The product to be offered will be a high performance instrument reader system,
referred to as the 'HP System.'  As per accepted industry practice, the HP
System will be built in two stages: A functional prototype, referred to as the
'Beta Model,' to be built in small quantities primarily for internal use and
testing only; and a fully tested product, referred to as the 'Production Model.'
The Beta Model and the Production Model will be based upon the following
specification.  This specification is recognized by both MTX and HP to not
define a complete product, but rather to specify important goals  upon which to
base the initial product offering and may be subject to modification by the PMC.


[                                                                              
                                        *  
                                                                              ]

                              COMPANY CONFIDENTIAL


                                                                               1
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                                    TREATMENT
                                    REQUESTED

[ 






                                       * 






                                                                              ]




                              COMPANY CONFIDENTIAL

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<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED

[ 







                                       * 






                                                                              ]



                              COMPANY CONFIDENTIAL

                                                                               3

<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED


[ 






                                       * 






                                                                              ]



                              COMPANY CONFIDENTIAL

                                                                               4

<PAGE>


                                   CONFIDENTIAL
                                    TREATMENT 
                                    REQUESTED


[ 


                                       * 


                                                                              ]


BETA MODEL

The objectives of the Beta Model are to demonstrate that the basic functionality
of the product design meets the above specifications, and to provide readers for
MTX and HP internal use for other studies as early as possible.  Definition of
Beta Model completion and quantities are described in the Collaboration
Agreement.  

PRODUCTION MODEL

The objective of the Production Model is to provide HP and MTX with a high
performance low cost reader system that is tailored for both the bioanalytical
and the biomedical research markets.  The Production Model will be based upon
technologies that the product development team feel present the lowest risk
means for meeting the product specification, as well as technologies from
research as specified by the RMC, and also any additional technology that either
HP or MTX has developed independently that each believes would be an appropriate
contribution.

The product development team will be able to obtain the services of the research
team to work on specific problems in order to meet product goals.  

COMMITTEES

RESEARCH MANAGEMENT COMMITTEE

The RMC will be responsible for specifying and reviewing the collaborative
research required to provide technology for the Production Model and possible
subsequent generations of the HP System.   [ *                              
                                                                              
                                                                              
                                                                              
                                                            ]

                              COMPANY CONFIDENTIAL

                                                                               5

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                                   CONFIDENTIAL
                                    TREATMENT 
                                    REQUESTED


[                                             *                               
                                              ]




PRODUCT MANAGEMENT COMMITTEE

The PMC will be responsible for overseeing the specification and development of
the HP System and planning for possible subsequent generations of the HP System.
 [ * ]



                              COMPANY CONFIDENTIAL


                                                                               6

<PAGE>

                                  CONFIDENTIAL 
                                    TREATMENT
                                    REQUESTED


AREAS OF WORK

The overall collaborative work is addressed in two parts:  underlying technology
research and development, and product development.  The work can be further
partitioned into research and development on the instrument, the chip, and the
chemistries at the chip/instrument interface.  For this collaboration, HP will
have responsibility for the product development and research for the instrument
[ *                                                                         ]. 
MTX will have responsibility for product development and research on the chip
and the algorithms necessary to transform the intensity data to identify the
chip specific bases in the target nucleic acid.  There will  be  collaboration
in the areas of the interface chemistries and the system user interface
involving both personnel from both MTX and HP.   A plan for implementation of an
API for experimental protocols will be the responsibility of the PMC. 

The resources described below are believed by both parties to be that which is
necessary to staff and complete the work.  If it is shown that further resources
are required to successfully meet the collaboration's goals, HP will make every
effort to provide those resources.  

RESEARCH

CHEMISTRY AND HYBRIDIZATION

[ * ]


                              COMPANY CONFIDENTIAL


                                                                               7

<PAGE>

                                  CONFIDENTIAL 
                                   TREATMENT
                                   REQUESTED

HP will have a supporting staff of engineers and technicians to assist in
construction and execution of experiments. 
 
INSTRUMENTATION

[ * ]

CHIP SUPPLY FOR THE DEVELOPMENT PROGRAM

[ * ]

PRODUCT DEVELOPMENT

The HP System will consist of an HP designed instrument with both onboard and
remote software.   It will be compatible with MTX designed image analysis
software, and a commercially available Intel based personal computer. [ * ]

[ * ]

A product development team will be staffed to define the product specification
and execute the product.  HP will staff a product development team as is typical
for this type and complexity of instrument. [ * ]


MANUFACTURING

[ * ]


                              COMPANY CONFIDENTIAL

                                                                               8


<PAGE>


                                   CONFIDENTIAL
                                    TREATMENT 
                                    REQUESTED


[                                  *                             ]

STAFFING

As described above, the total staff for the MTX/HP collaboration would be
approximately as follows:


[ 




                                       * 




                                                                              ]


Payment for MTX staff by HP, and makeup of staff will be per the terms in the
collaboration agreement.

SCHEDULE

In order to proceed in a timely fashion, the RMC and PMC will meet within 2
weeks after the date when Collaboration Agreement is signed to develop schedules
for execution of the first set of tasks for each committee.



                              COMPANY CONFIDENTIAL


                                                                               9


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                                   TREATMENT
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                                   EXHIBIT  B

The following list is for both Parties:

[ * ]


<PAGE>

                                  CONFIDENTIAL 
                                   TREATMENT
                                   REQUESTED


                                   EXHIBIT  D

List of Cross-Licensees:

[ * ]





 

<PAGE>



                        DEVELOPMENT AND SUPPLY AGREEMENT

                                     between

                                AFFYMETRIX, INC.

                                       and

                            GENETICS INSTITUTE, INC. 



<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

                                TABLE OF CONTENTS


                                                                      Page
                                                                      ----

INTRODUCTION  . . . . . . . . . . . . . . . . . . . . . . . . . . .     1

ARTICLE I.  DEFINITIONS 

            1.1    Additional Gene Sequences  . . . . . . . . . . .     2
            1.2    Affiliate. . . . . . . . . . . . . . . . . . . .     2
            1.3    Chip Patent Rights . . . . . . . . . . . . . . .     2
            1.4    Confidential Information . . . . . . . . . . . .     3
            1.5    Copyrights . . . . . . . . . . . . . . . . . . .     3
            1.6    Contract Year. . . . . . . . . . . . . . . . . .     3
            1.7    [     *     ]  . . . . . . . . . . . . . . . . .     3
            1.8    [     *     ]  . . . . . . . . . . . . . . . . .     3
            1.9    DNA Chips. . . . . . . . . . . . . . . . . . . .     4
            1.10   Distributor. . . . . . . . . . . . . . . . . . .     4
            1.11   DNA Chip Products. . . . . . . . . . . . . . . .     4
            1.12   DNA Chip Technology. . . . . . . . . . . . . . .     4
            1.13   Exclusivity Period . . . . . . . . . . . . . . .     4
            1.14   Full-Time Equivalent . . . . . . . . . . . . . .     4
            1.15   Fully-Loaded Manufacturing Cost. . . . . . . . .     5
            1.16   Gene Expression Screening. . . . . . . . . . . .     5
            1.17   Gene Fields. . . . . . . . . . . . . . . . . . .     6
            1.18   Gene Patent Rights . . . . . . . . . . . . . . .     6
            1.19   GI Novel Gene Discovery Field. . . . . . . . . .     6
            1.20   GI Technology. . . . . . . . . . . . . . . . . .     6
            1.21   Joint Technology . . . . . . . . . . . . . . . .     6
            1.22   Know-How . . . . . . . . . . . . . . . . . . . .     6
            1.23   Milestone. . . . . . . . . . . . . . . . . . . .     6
            1.24   MTX Technology . . . . . . . . . . . . . . . . .     7
            1.25   Net Sales. . . . . . . . . . . . . . . . . . . .     7
            1.26   Novel Compounds. . . . . . . . . . . . . . . . .     9
            1.27   Novel Gene List. . . . . . . . . . . . . . . . .     9
            1.28   Novel Human Therapeutic Compounds. . . . . . . .     9
            1.29   Other DNA Chip Products. . . . . . . . . . . . .     10
            1.30   Party. . . . . . . . . . . . . . . . . . . . . .     10
            1.31   Patent Rights. . . . . . . . . . . . . . . . . .     10
            1.32   Performance Bonus. . . . . . . . . . . . . . . .     11
            1.33   Probes . . . . . . . . . . . . . . . . . . . . .     11
            1.34   Products . . . . . . . . . . . . . . . . . . . .     11
            1.35   Projects . . . . . . . . . . . . . . . . . . . .     11
            1.36   Project Director . . . . . . . . . . . . . . . .     11
            1.37   Research Management Committee. . . . . . . . . .     11
            1.38   Sublicensee. . . . . . . . . . . . . . . . . . .     11
            1.39   [     *     ]. . . . . . . . . . . . . . . . . .     12
            1.40   [     *     ]. . . . . . . . . . . . . . . . . .     12
            1.41   Valid Claim. . . . . . . . . . . . . . . . . . .     12
            1.42   Workplan . . . . . . . . . . . . . . . . . . . .     12


                                       i

<PAGE>


                        CONFIDENTIAL TREATMENT REQUESTED

ARTICLE II.  THE PROJECT 

            2.1    Purpose. . . . . . . . . . . . . . . . . . . . .     12
            2.2    Gene Fields. . . . . . . . . . . . . . . . . . .     13
            2.3    Term . . . . . . . . . . . . . . . . . . . . . .     16
            2.4    Staffing . . . . . . . . . . . . . . . . . . . .     17
            2.5    Research Management Committee. . . . . . . . . .     17
            2.6    Facilities . . . . . . . . . . . . . . . . . . .     18
            2.7    Inspection . . . . . . . . . . . . . . . . . . .     18
            2.8    Patent and Confidential Information Agreements .     18
            2.9    Reports. . . . . . . . . . . . . . . . . . . . .     18


ARTICLE III.  PROJECT FUNDING

            3.1    Development Efforts of MTX . . . . . . . . . . .     19
            3.2    Funding of Full-Time Equivalents . . . . . . . .     19
            3.3    Capital Funding for Equipment. . . . . . . . . .     20
            3.4    Other Expenditures . . . . . . . . . . . . . . .     21
            3.5    Performance Bonuses. . . . . . . . . . . . . . .     21
            3.6    Records. . . . . . . . . . . . . . . . . . . . .     22


ARTICLE IV.  OWNERSHIP AND USE OF TECHNOLOGY

            4.1    Ownership of Developments. . . . . . . . . . . .     22
            4.2    Licenses . . . . . . . . . . . . . . . . . . . .     23
            4.3    Rights of MTX to Joint Technology outside the
                     Project. . . . . . . . . . . . . . . . . . . .     24
            4.4    Rights of GI to Joint Technology outside the
                     Project. . . . . . . . . . . . . . . . . . . .     25


ARTICLE V.  EXCLUSIVITY

            5.1    General Rights . . . . . . . . . . . . . . . . .     25
            5.2    Use of Proprietary Gene Sequences. . . . . . . .     25
            5.3    Use of Probes. . . . . . . . . . . . . . . . . .     26
            5.4    GI Exclusivity on Collaborations Involving
                     the [     *     ] . . . . . . . . . . .. . . .     26
            5.5    GI Exclusivity on Collaboration Involving the
                     [     *     ]  . . . . . . . . . . . . . . . .     27
            5.6    GI Exclusivity on collaborations Involving the
                     GI Novel Gene Discovery Field. . . . . . . . .     27
            5.7    Limitations on Product Sales Involving the 
                     Gene Fields. . . . . . . . . . . . . . . . . .     29
            5.8    Project Refund and Payment Adjustment. . . . . .     29
            5.9    Bilateral Communication. . . . . . . . . . . . .     29


                                      ii

<PAGE>

ARTICLE VI.  BENCHMARKS AND ROYALTIES

            6.1    Royalties to GI. . . . . . . . . . . . . . . . .     30
            6.2    Benchmarks to MTX for Novel Human Therapeutic
                     Compounds. . . . . . . . . . . . . . . . . . .     32
            6.3    Royalties to MTX for Novel Human Therapeutic
                     Compounds. . . . . . . . . . . . . . . . . . .     33
            6.4    Reports and Payment. . . . . . . . . . . . . . .     37
            6.5    Foreign Royalties. . . . . . . . . . . . . . . .     38
            6.6    Taxes. . . . . . . . . . . . . . . . . . . . . .     38
            6.7    Records. . . . . . . . . . . . . . . . . . . . .     39


ARTICLE VII.  SUPPLY

            7.1    Supply of DNA Chip Products. . . . . . . . . . .     39
            7.2    Supply Price for DNA Chip Products . . . . . . .     40
            7.3    Forecasts and Adequate Supply of DNA Chip
                     Products . . . . . . . . . . . . . . . . . . .     40
            7.4    Supply of Other DNA Chip Products. . . . . . . .     41
            7.5    Records. . . . . . . . . . . . . . . . . . . . .     41


ARTICLE VIII.  PATENT PROSECUTION AND INFRINGEMENT RIGHTS

            8.1    Responsibility for Patenting of Technology . . .     42
            8.2    Infringement . . . . . . . . . . . . . . . . . .     43
            8.3    Claimed Infringement . . . . . . . . . . . . . .     47


ARTICLE IX.  CONFIDENTIAL INFORMATION 

            9.1    Treatment of Confidential Information. . . . . .     48
            9.2    Release from Restrictions. . . . . . . . . . . .     48
            9.3    Publications . . . . . . . . . . . . . . . . . .     49


ARTICLE X.  TERMINATION

            10.1   Term . . . . . . . . . . . . . . . . . . . . . .     50
            10.2   Termination Due to Lack of Feasibility . . . . .     50
            10.3   Termination Due to Lack of Progress. . . . . . .     52
            10.4   Termination Due to an Impasse. . . . . . . . . .     52
            10.5   Termination of Agreement for Breach. . . . . . .     54
            10.6   Survival of Obligations; Return of Confidential
                     Information. . . . . . . . . . . . . . . . . .     54


ARTICLE XI.  INDEMNIFICATION AND LIABILITY LIMITATIONS

            11.1   Product Liability Indemnification. . . . . . . .     55


                                      iii

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

            11.2   Liability. . . . . . . . . . . . . . . . . . . .     57


ARTICLE XII.  EXPORT

            12.1   Acknowledgement. . . . . . . . . . . . . . . . .     58
            12.2   Written Assurance. . . . . . . . . . . . . . . .     58


ARTICLE XIII.  MISCELLANEOUS

            13.1   Representations and Warranties of MTX  . . . . .     59
            13.2   Publicity. . . . . . . . . . . . . . . . . . . .     60
            13.3   Assignment . . . . . . . . . . . . . . . . . . .     60
            13.4   Governing Law. . . . . . . . . . . . . . . . . .     60
            13.5   Force Majeure. . . . . . . . . . . . . . . . . .     60
            13.6   Waiver . . . . . . . . . . . . . . . . . . . . .     61
            13.7   Notices. . . . . . . . . . . . . . . . . . . . .     61
            13.8   No Agency. . . . . . . . . . . . . . . . . . . .     62
            13.9   Entire Agreement . . . . . . . . . . . . . . . .     62
            13.10  Headings . . . . . . . . . . . . . . . . . . . .     62
            13.11  Severability . . . . . . . . . . . . . . . . . .     63
            13.12  Successors and Assigns . . . . . . . . . . . . .     63
            13.13  Third Parties. . . . . . . . . . . . . . . . . .     63
            13.14  Counterparts . . . . . . . . . . . . . . . . . .     63


SCHEDULES

            Schedule A - Workplan, Milestones and Performance Bonuses
            Schedule B - [     *     ]
            Schedule C - Contract Year l Budget


                                      iv

<PAGE>

                        DEVELOPMENT AND SUPPLY AGREEMENT

    AGREEMENT effective as of November 15, 1994 between AFFYMETRIX, INC., a 
California corporation having its principal place of business at 3380 Central 
Expressway, Santa Clara, California 95051 (hereinafter referred to as "MTX") 
and GENETICS INSTITUTE, INC., a Delaware corporation, having its principal 
place of business at 87 CambridgePark Drive, Cambridge, Massachusetts 02140 
(hereinafter referred to as "GI").

                                  INTRODUCTION

         1.   MTX has research and development facilities and experienced 
scientists, engineers, technical associates and assistants and other 
personnel and has rights to and has developed certain DNA chip based 
technology.

         2.   GI has research and development facilities and experienced 
scientists, clinicians, engineers, technical associates and assistants and 
other personnel which enable it to conduct research and development 
activities in the area of biotechnology and the application thereof to the 
development, production and manufacture, registration and marketing of 
biotechnology based pharmaceutical products.

         3.   MTX and GI desire to enter into a collaboration for the purpose 
of developing DNA chip based products that will assist GI in the discovery of 
novel human therapeutic compounds and novel uses of human therapeutic 
compounds.

                                       1

<PAGE>

         4.   MTX and GI are willing, for the consideration and on the terms 
set forth herein, to enter into such a collaboration.

         In consideration of the mutual covenants and promises contained
in this Agreement and other good and valuable consideration, MTX and GI agree as
follows:

                             ARTICLE I.  DEFINITIONS

         As used in this Agreement, the following terms, whether used in
the singular or plural, shall have the following meanings:

         1.1.  "ADDITIONAL GENE SEQUENCES" is defined in Section 2.2 of
this Agreement.

         1.2.  "AFFILIATE" means any corporation, company, partnership,
joint venture and/or firm which controls, is controlled by or is under common
control with a Party.  For purposes of this Section 1.2, "control" shall mean
direct or indirect ownership of at least 50% of the equity of an entity.

         1.3.  "CHIP PATENT RIGHTS" means any and all patents and patent
applications of a Party (whether solely or jointly owned) which specifically
relate to the design, engineering, manufacture or use of DNA Chips and are
reasonably useful or necessary or required to develop, use, manufacture,
distribute and/or sell DNA Chips.  The Parties acknowledge that it is not
anticipated that GI will develop any Chip Patent Rights.  Notwithstanding the
foregoing, for purposes of clarification, but without limitation, the Parties
further acknowledge that any and all chip assays and Probes developed by the
Parties in or for use in the Project shall not constitute Chip Patent Rights.


                                       2

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED


         1.4.  "CONFIDENTIAL INFORMATION" means (a) all proprietary
information and materials, patentable or otherwise, of a Party which is
disclosed by or on behalf of such Party to the other Party, 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, which do not fall within any of the
exceptions set forth in Sections 9.2(a), (b) and (c) of this Agreement and (b)
any other information designated by the disclosing Party to the other Party as
confidential or proprietary, whether or not related to the Project, which does
not fall within any of the exceptions set forth in Sections 9.2(a), (b) or (c)
of this Agreement. 

         1.5.  "COPYRIGHTS" means all copyrights of a Party (whether solely 
or jointly owned) which (a) relate to technology used or developed in the 
Project and (b) are reasonably useful or necessary or are required to 
develop, use, manufacture, distribute and/or sell DNA Chip Products.

         1.6.  "CONTRACT YEAR" means any year commencing on November 15 and 
ending on November 14.

         [     *     ]


                                       3

<PAGE>

         1.9.  "DNA CHIPS" means any and all DNA chips developed in the
Project, the use, making or selling of which (a) is covered by a Valid Claim of
any of the Patent Rights, (b) is covered by any of the Copyrights and/or (c)
embodies any Know-How.

         1.10.  "DISTRIBUTOR" means a third party which is not an Affiliate 
or Sublicensee of a Party and which is a distributor, wholesaler or other 
entity purchasing Products from a Party or an Affiliate or Sublicensee for 
resale.  

         1.11.  "DNA CHIP PRODUCTS" means DNA Chips, hybridization platforms 
developed in the Project, DNA chip readers developed in the Project, software 
developed in the Project and/or any and all other products developed in the 
Project, the use, making or selling of which (a) is covered by a Valid Claim 
of any of the Patent Rights, (b) is covered by any of the Copyrights and/or 
(c) embodies any Know-How.

         1.12.  "DNA CHIP TECHNOLOGY" means the Copyrights, Know-How
and/or Patent Rights.

         1.13.  "EXCLUSIVITY PERIOD" means the period commencing on the
date of this Agreement and ending on the fifth anniversary of the date of this
Agreement.

         1.14.  "FULL-TIME EQUIVALENT" means the equivalent of a full-time
technical employee's work time over a 12-month period (including normal
vacations and holidays); the portion of a Full-Time Equivalent year devoted by a
technical employee to the Project shall be determined by dividing the number of
days during any 12-month period devoted by such employee to the Project by the
total 


                                       4

<PAGE>

number of working days during the 12-month period.  As used in this Section 
1.14, a "technical employee" shall include any scientist, engineer, technical 
associate or assistant and/or other personnel (whether an employee or 
consultant) assigned to the Project.

         1.15.  "FULLY-LOADED MANUFACTURING COST" means (a) costs directly
attributable to manufacturing, quality assurance and quality control related to
a unit of product (i.e., those costs which vary with production), including, but
not limited to, direct labor and benefit expenses for manufacturing, and
consumable bulk and other production materials, as determined in accordance with
United States generally accepted cost accounting practices, plus (b) fixed
manufacturing overhead costs allocable to the product based on the actual
utilization of the manufacturing facility, including but not limited to, direct
benefit and labor expenses for technical services and support services,
depreciation, maintenance and repairs and insurance costs associated with such
utilization of the manufacturing facility, as determined in accordance with
United States generally accepted cost accounting practices, and less (c) costs
otherwise paid for by GI pursuant to Sections 3.2 and 3.3 of this Agreement.

         1.16.  "GENE EXPRESSION SCREENING" means the use of DNA chip
based technology as a research tool to measure the presence and/or levels of
nucleic acid sequences for the purpose of discovering novel human therapeutic
compounds and novel uses of human therapeutic compounds which, in each case, are
encoded by or regulated by the genes (or their interspecies homologues) probed


                                       5

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

for on the DNA chip or are gene products identified by the elimination of
proteins encoded by the nucleic acid sequences on the DNA chip.  

         1.17.  "GENE FIELDS" means the [     *     ]

         1.18.  "GENE PATENT RIGHTS" means all patents and patent
applications of a Party (whether solely or jointly owned) which relate to Novel
Compounds or the genes related thereto and are reasonably useful or necessary or
are required to develop, use, manufacture, distribute and/or sell Novel
Compounds.  The Parties acknowledge that it is not anticipated that MTX will
develop any Gene Patent Rights.  

         1.19.  "GI NOVEL GENE DISCOVERY FIELD" is defined in Section 2.2 of 
this Agreement.

         1.20.  "GI TECHNOLOGY" is defined in Section 4.1 of this Agreement.

         1.21.  "JOINT TECHNOLOGY" is defined in Section 4.1 of this 
Agreement.

         1.22.  "KNOW-HOW" means all information, patentable or otherwise, of 
a Party (whether solely or jointly owned) which (a) is used or developed in 
the Project and (b) is reasonably useful or necessary or is required to 
develop, use, manufacture, distribute and/or sell DNA Chip Products.

         1.23.  "MILESTONE" means any of the milestones set forth in SCHEDULE 
A to this Agreement.


                                       6

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

         1.24.  "MTX TECHNOLOGY" is defined in Section 4.1 of this Agreement.

         1.25.  "NET SALES" means the aggregate United States Dollar 
equivalent of [     *     ] less (a) [     *     ]. Net Sales shall not 
include [     *     ].  If a Party or an Affiliate or Sublicensee sells 
Products to a Distributor, Net Sales shall be deemed to be [     *     ].  In 
the event that a Party or any of its Affiliates or Sublicensees shall make 
any transfer of Products to third parties for other than monetary value in 
whole or in part, such transfer shall be considered a sale hereunder for 
accounting and royalty purposes.  


                                       7

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

Net Sales for any such transfers shall be determined on a country-by-country 
basis and shall be [     *     ]. Notwithstanding the foregoing, no transfer 
of Products for test or developmental purposes or as samples shall be 
considered a sale hereunder for accounting and royalty purposes unless such 
transfer is for monetary value.  If Products are sold as part of a system, 
package or combination product, Net Sales shall be [     *     ].  If such 
Product is not sold separately, [     *     ].  Without limiting the 
generality of the foregoing, [     *     ].


                                       8

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

         1.26.  "NOVEL COMPOUNDS"  means proteins (or any peptides or domain 
deleted, modified (i.e., by chemical or enzymatic cleavage or otherwise), 
variant or mutant forms thereof) derived from novel genes discovered by GI or 
its designated Affiliates through the use of DNA Chip Products or proteins 
(or any peptides or domain deleted, modified (i.e., by chemical or enzymatic 
cleavage or otherwise), variant or mutant forms thereof) for which novel uses 
are discovered by GI or its designated Affiliates through the use of DNA Chip 
Products.  For purposes of this definition, if a DNA Chip Product was useful 
to GI or its designated Affiliates in the discovery of the novel gene or 
novel use, the related protein (or peptide or domain deleted, modified (i.e., 
by chemical or enzymatic cleavage or otherwise), variant or mutant form 
thereof) shall be deemed to have been discovered through the use of DNA Chip 
Products.  Novel Compounds shall not include [     *     ] for which novel 
uses are discovered by GI or its designated Affiliates through the use of DNA 
Chip Products. 

         1.27.  "NOVEL GENE LIST" is defined in Section 2.2 of this Agreement.

         1.28.  "NOVEL HUMAN THERAPEUTIC COMPOUNDS" means human 
therapeutic proteins (or any peptides or domain deleted, modified (i.e., by 
chemical or enzymatic cleavage or otherwise), variant or mutant forms 
thereof) derived from novel genes discovered by GI or its designated 
Affiliates through the use of DNA Chip Products or proteins (or any peptides 
or domain deleted, modified (i.e., by 


                                       9

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

chemical or enzymatic cleavage or otherwise), variant or mutant forms 
thereof) for which novel human therapeutic uses are discovered by GI or its 
designated Affiliates through the use of DNA Chip Products.  For purposes of 
this definition, if a DNA Chip Product was useful to GI or its designated 
Affiliates in the discovery of the novel gene or novel use, the related 
protein (or peptide or domain deleted, modified (i.e., by chemical or 
enzymatic cleavage or otherwise), variant or mutant form thereof) shall be 
deemed to have been discovered through the use of DNA Chip Products.  Novel 
Human Therapeutic Compounds shall not include [     *     ] for which novel 
human therapeutic uses are discovered by GI or its designated Affiliates 
through the use of DNA Chip Products.

         1.29.  "OTHER DNA CHIP PRODUCTS"  means DNA chips developed
outside the Project, hybridization platforms developed outside the Project, DNA
chip readers developed outside the Project, software developed outside the
Project and/or any and all other products developed outside the Project, the
use, making or selling of which (a) is covered by a Valid Claim of any of the
Patent Rights, (b) is covered by any of the Copyrights and/or (c) embodies any
Know-How.

         1.30.  "PARTY" means MTX or GI; "PARTIES" means MTX and GI.

         1.31.  "PATENT RIGHTS" means all  patents and patent applications
of a Party (whether solely or jointly owned) which (a) relate to technology used
or developed in the Project and (b) are 


                                       10

<PAGE>

reasonably useful or necessary or are required to develop, use, manufacture, 
distribute and/or sell DNA Chip Products.

         1.32.  "PERFORMANCE BONUS" means any of the performance bonuses set 
forth in SCHEDULE A to this Agreement.

         1.33.  "PROBES" means the oligos selected for use in the DNA Chips.

         1.34.  "PRODUCTS" means either (a) DNA Chip Products, (b) Novel
Human Therapeutic Compounds or (c) Other DNA Chip Products.

         1.35.  "PROJECT" means the research and development program jointly 
conceived, planned, organized, controlled and performed by MTX and GI 
pursuant to the Workplan and this Agreement.

         1.36.  "PROJECT DIRECTOR" means either of the senior scientists for 
the Project designated from time to time by MTX or GI.

         1.37.  "RESEARCH MANAGEMENT COMMITTEE" means the committee
consisting of two members from each of MTX and GI, as designated by MTX and GI
from time to time, which committee shall be responsible for planning and
overseeing the Project.

         1.38.  "SUBLICENSEE" means, with respect to MTX, a third party
which is not an Affiliate of MTX and to whom MTX has granted a license or
sublicense to develop, use, manufacture, distribute and/or sell DNA Chip
Products and/or Other DNA Chip Products and, with respect to GI, a third party
which is not an Affiliate of GI and to whom GI has granted a license or
sublicense to develop, use, manufacture, distribute and/or sell Novel Human
Therapeutic Compounds discovered by GI or its designated Affiliates.  A third


                                       11

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

party which is not an Affiliate of GI and which purchases Novel Human
Therapeutic Compounds in bulk form from GI shall be deemed to be a Sublicensee
of GI and not a Distributor of GI. 

               [     *     ]

         1.41.  "VALID CLAIM" means a claim of an unexpired patent which 
shall not have been withdrawn, canceled or disclaimed, nor held invalid or 
unenforceable by a court of competent jurisdiction in an unappealed or 
unappealable decision, or the claim of a patent application which has not 
been on file for more than five years.

         1.42.  "WORKPLAN" means the workplan set forth in SCHEDULE A to this 
Agreement.
                                        
                            ARTICLE II.  THE PROJECT

         2.1. PURPOSE.  The purpose of the Project shall be to collaborate
on the further development and application of MTX's existing DNA Chip Technology
to Gene Expression Screening in the Gene Fields.  With respect to each Gene
Field, MTX and GI shall develop one or more DNA Chips and related DNA Chip
Technology.  Each of the Parties agrees to undertake the Project on a best
efforts basis with the objective of completing the Milestones in accordance with
the Workplan and by the third anniversary of the date

                                      12

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

of this Agreement.  The
Parties acknowledge that it may be necessary to make changes to the Milestones
and the Workplan during the course of the Project.  All material changes to the
Milestones and the Workplan shall require the written consent of both Parties.

         2.2.  GENE FIELDS.

         (a)  During the initial term of the Project, GI shall furnish MTX 
with a list (the "[     *     ] List") of up to [     *     ] full-length 
and/or partial gene sequences representing [     *     ] genes and genes 
[     *     ].  In the case of partial gene sequences, GI shall reasonably 
believe that such gene sequences uniquely define specific genes.  As part of 
the Project, the Parties shall identify and select Probes directed to these 
gene sequences for inclusion in one or more DNA Chips.  With respect to each 
such gene sequence, until such time as the Parties commence the 
identification and selection of the Probes for such gene sequence, GI shall 
have the right to substitute a full-length and/or partial gene sequence 
representing a [     *     ]gene or gene [     *     ] for such gene 
sequence, provided that the number of gene sequences on the [     *     ] 
never exceeds [     *     ].  Thereafter, GI shall have the right to make 
substitutions only with the consent of the Research Management Committee and 
only so long as the number of gene sequences on the [     *     ] List never 
exceeds [     *     ].  The gene sequences appearing on the [     *     ] 
List are referred to in this Agreement as the "[     *     ] Field."  
Notwithstanding the foregoing, in the event that, prior to the completion of 
the DNA Chips for the [     *     ] 

                                      13

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED


Field, MTX is in the process of 
negotiating a collaboration with a third party other than GI which could 
involve the [     *     ] 


Field, MTX, at its option, may notify GI in writing and GI shall finalize the 
[     *     ] List within forty-five (45) days of such notification.

         (b)  During the initial term of the Project, GI shall furnish MTX 
with a list (the "[     *     ] List") of approximately [     *     ] 
full-length and/or partial gene sequences representing genes in the 
[     *     ].  In the case of partial gene sequences, GI shall reasonably 
believe that such gene sequences uniquely define specific genes.  As part of 
the Project, the Parties shall identify and select Probes directed to these 
gene sequences for inclusion in one or more DNA Chips.  Further, as part of 
the Project, the Parties shall identify and select [     *     ] representing 
[     *     ] within the [     *     ] for inclusion in one or more DNA 
Chips.  The Research Management Committee shall determine the appropriate 
number of [     *     ] taking into account the desires of GI, the technical 
feasibility of including the number desired by GI and the funding constraints 
on the Parties. With respect to each gene sequence on the [     *     ] List, 
until such time as the Parties commence the identification and selection of 
the Probes for such gene sequence, GI shall have the right to substitute a 
full-length and/or partial gene sequence representing a gene in the 
[     *     ] for such gene sequence.  Thereafter, GI shall have the right to 
make substitutions only with the consent of the Research Management 
Committee.  To the extent that GI discovers full-length and/or 

                                      14

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED


partial gene 
sequences representing genes in the [     *     ] subsequent to the 
commencement of the identification and selection of the Probes for the DNA 
Chips for the [     *     ], GI shall have the right to identify and have 
such full-length and/or partial gene sequences included in the [     *     ] 
List.  MTX shall have no obligation, however, to develop DNA Chips relating to 
these subsequently identified gene sequences.

         (c)  During the initial term of the Project, GI shall furnish MTX 
with a list (the "Novel Gene List") of up to [     *     ] full-length and/or 
partial gene sequences representing genes identified as part of GI's factor 
discovery program.  In the case of partial gene sequences, GI shall 
reasonably believe that such gene sequences uniquely define specific genes.  
As part of the Project, the Parties shall identify and select Probes directed 
to these gene sequences for inclusion in one or more DNA Chips.  With respect 
to each such gene sequence, until such time as the Parties commence the 
identification and selection of the Probes for such gene sequence, GI shall 
have the right to substitute a full-length  and/or partial gene sequence 
representing a gene identified as part of GI's factor discovery program for 
such gene sequence, provided that the number of gene sequences on the Novel 
Gene List never exceeds [     *     ].  Thereafter, GI shall have the right 
to make substitutions only with the consent of the Research Management 
Committee and only so long as the number of gene sequences on the Novel Gene 
List never exceeds [     *     ].  The gene sequences appearing on the Novel 
Gene List are referred to in this  


                                       15

<PAGE>

Agreement as the "GI Novel Gene Discovery Field."  Notwithstanding the 
foregoing, in the event that, prior to the completion of the DNA Chips for 
the GI Novel Gene Discovery Field, MTX is in the process of negotiating a 
collaboration with a third party other than GI which could involve the GI 
Novel Gene Discovery Field, MTX, at its option, may notify GI in writing and 
GI shall finalize the Novel Gene List within forty-five (45) days of such 
notification. 

         (d)  During the term of the Project and as part of the Project, GI 
shall have the right to propose the production of DNA Chips for gene 
sequences in addition to those included in the Gene Fields subject to the 
technical feasibility of producing such DNA Chips and the negotiation of 
mutually acceptable terms.   The additional gene sequences included in any 
such DNA Chips shall be referred to in this Agreement as the "Additional Gene 
Sequences."    

         (e)  During the term of the Project, MTX and GI may agree on other 
gene fields to be pursued as part of the Project.  Any such expansion of the 
Project shall include terms mutually acceptable to MTX and GI.  MTX agrees to 
consider in good faith any proposals relating to other gene fields made by 
GI.            

         2.3.  TERM.  The Project will be for an initial term of up to three 
years and may be extended by mutual agreement of MTX and GI.  In the event 
that the Milestones are achieved prior to the expiration of three years, MTX 
and GI will determine at such time whether continued meaningful research and 
development can be conducted for the remainder of the three years.  If MTX 
and GI determine that continued meaningful research and development can be 


                                       16

<PAGE>

conducted, they shall use best efforts to agree on additional milestones for 
the remainder of the three years.  The initial term of the Project shall 
expire on the earlier of (a) the third anniversary of the date of this 
Agreement or (b) the achievement of the Milestones.

         2.4.  STAFFING.  Each Party shall, as soon as practicable, assemble 
a team of scientists, engineers, technical associates and/or assistants and 
shall designate a Project Director to conduct the activities allocated to 
such Party under the Workplan.

         2.5.  RESEARCH MANAGEMENT COMMITTEE.  The Project will be managed by 
a Research Management Committee which  committee shall be responsible for 
planning and overseeing the Project.  The Research Management Committee shall 
be composed of two representatives from each of MTX and GI.  The Research 
Management Committee shall be responsible for refining the Workplan, 
allocating efforts between MTX and GI, and establishing and approving annual 
budgets for the Workplan (within the limits of Article III of this Agreement) 
for the second and third Contract Years.  The annual budget for the first 
Contract Year is set forth in SCHEDULE C to this Agreement.  The Research 
Management Committee shall meet a minimum of twice per Contract Year during 
the term of the Project.  The site of such meetings shall alternate between 
the offices of MTX and GI (or any other site mutually agreed upon by the 
Parties).  With respect to all matters to be decided by the Research 
Management Committee, the decision of a majority of all of the members of the 
Research Management Committee shall be 


                                       17

<PAGE>

determinative. All meetings of the Research Management Committee shall be 
summarized in writing and sent to both Parties.     

         2.6.  FACILITIES.  The Project shall be conducted at and/or 
coordinated from the facilities of each Party under the supervision and 
direction of its Project Director.  Each Party shall be responsible for the 
administrative management and fiscal control of the activities for the 
Project conducted from its facilities.

         2.7.  INSPECTION.  Each Party shall have the right to arrange for 
its employees and consultants involved in the Project to visit the other 
Party's facilities and to discuss the Workplan and its results in detail with 
the technical personnel of the other Party, provided that visits shall be on 
mutually convenient dates and during mutually convenient business hours and 
shall not unreasonably interrupt the operations of the other Party.

         2.8.  PATENT AND CONFIDENTIAL INFORMATION AGREEMENTS.  Each Party 
shall require each of its employees and consultants assigned to the Project 
to execute an agreement for the assignment of inventions and for the 
protection of Confidential Information in such reasonable form as may from 
time to time be used by such Party and approved by the other Party.

         2.9.  REPORTS.  MTX and GI shall each provide the Research 
Management Committee and the other Party with written progress reports 
summarizing the technical progress of the Project on a semi-annual basis 
within thirty (30) days after the end of each May 15 and November 15 until 
the expiration of the term of the Project.  Each Party shall also provide the 
Research Management Committee and 


                                       18

<PAGE>

the other Party with additional oral progress reports as requested from time 
to time by the Research Management Committee or the other Party.

                          ARTICLE III.  PROJECT FUNDING

         3.1.  DEVELOPMENT EFFORTS OF MTX.  MTX and GI shall provide the 
technical support of the following numbers of Full-Time Equivalents during 
the initial three years of the Project:

                    Contract
                      Year                 MTX          GI
                    --------               ---          --
                       1              [     *     ][     *     ]
                       2              [     *     ][     *     ]
                       3              [     *     ][     *     ]

With respect to GI, the Parties acknowledge the fact that the technical 
support of [     *     ] Full-time Equivalents may not be required of GI 
during the first Contract Year.  GI shall provide such technical support as 
is actually required up to [     *     ]Full-Time Equivalents.  The exact 
commitment of MTX for the second and third Contract Years shall be determined 
by the Research Management Committee and included in the annual budgets for 
such years.

         3.2.  FUNDING OF FULL-TIME EQUIVALENTS.  GI shall fund the technical 
support development efforts at MTX at a rate equal to [     *     ] per 
Full-Time Equivalent per Contract Year as follows:

                    Contract                    Minimum             Maximum
                      Year                      Funding             Funding
                    --------                    -------             -------
                       1                     [     *     ]       [     *     ]
                       2                     [     *     ]       [     *     ]
                       3                     [     *     ]       [     *     ]


                                       19

<PAGE>

Such [     *     ] is intended to represent the fully loaded costs of MTX.  
An advance of [     *     ] against payments due the first Contract Year and 
an advance of [     *     ] against payments due the second Contract Year 
shall be paid to MTX within ten (10) days of the execution of this Agreement. 
 The balance due for the first Contract Year shall be paid to MTX in four 
equal quarterly installments on the first day of each contract quarter during 
such Contract Year and the balance due for the second Contract Year shall be 
paid to MTX in four equal quarterly installments on the first day of each 
contract quarter during such Contract Year.  The funding for the third 
Contract Year shall be paid to MTX in four equal quarterly installments on 
the first day of each contract quarter during such Contract Year.  MTX shall 
present GI with an invoice for all amounts due and GI shall make payments 
against such invoices.  GI shall also fund the technical support development 
efforts at GI.

         3.3.  CAPITAL FUNDING FOR EQUIPMENT.  To the extent that such 
amounts are not covered in the payments made by GI to MTX pursuant to Section 
3.2 of this Agreement, GI shall fund a mutually agreeable allocation of the 
investment in equipment as is used by MTX in fulfilling its development 
efforts during the initial three years of the Project.  The Parties 
acknowledge that the estimated funding for the first Contract Year is zero.  
The estimated capital funding for each of the second and third Contract Years 
shall be determined by the Research Management Committee (taking into account 
the need to ensure adequate supply to GI) and included in 


                                       20

<PAGE>

the annual budgets for such years.  Any increases in excess of the estimated 
capital funding for any Contract Year shall be approved by the Research 
Management Committee.  Capital funding, whether part of the fully loaded 
costs set forth in Section 3.2 of this Agreement or the payments to be made 
pursuant to this Section 3.3, shall include capital expenditures for that 
portion of such purchased equipment as is used by MTX in the Project and that 
portion of the depreciation (based on a useful life of five years from the 
date of purchase of the equipment) on such existing equipment as is used by 
MTX in the Project.  The funding for each Contract Year shall be based on 
actual utilization and shall be paid to MTX in four equal quarterly 
installments within fifteen (15) days of the last day of each contract 
quarter during such Contract Year.  MTX shall present GI with an invoice for 
all amounts due and GI shall make payments against such invoices.  Any 
investment in equipment required to be made by GI to fulfill its development 
responsibilities shall be included in the annual budgets and shall be funded 
by GI.

         3.4.  OTHER EXPENDITURES.  Any and all other costs required to be 
incurred by each of MTX and GI in excess of the amounts set forth in Sections 
3.2 and 3.3 of this Agreement in order to fulfill its responsibilities under 
the Workplan and this Agreement, such as travel expenditures, shall be borne 
by the Party required to incur such costs.

         3.5.  PERFORMANCE BONUSES.  Within 30 days of the achievement of 
each Milestone (as satisfactorily evidenced to GI by MTX or by 


                                     21

<PAGE>

GI itself), GI shall pay to MTX the Performance Bonus for such Milestone set 
forth in SCHEDULE A.

         3.6.  RECORDS.  MTX shall keep true and accurate records to 
substantiate the expenditure of all funds paid to MTX by GI pursuant to 
Sections 3.2 and 3.3 of this Agreement.  Upon request from GI, MTX shall 
permit GI or its authorized representative to inspect such records in 
confidence in order to verify the expenditure of funds charged to GI.

                  ARTICLE IV.  OWNERSHIP AND USE OF TECHNOLOGY

         4.1.  OWNERSHIP OF DEVELOPMENTS.  MTX shall own all patent rights, 
copyrights and know-how developed solely by employees or consultants of MTX 
which do not incorporate Confidential Information belonging to GI even though 
use of GI's Confidential Information may have been incidental in such 
development (the "MTX Technology").  GI shall own all patent rights, 
copyrights and know-how developed solely by employees or consultants of GI 
which do not incorporate Confidential Information belonging to MTX even 
though use of MTX's Confidential Information may have been incidental in such 
development (the "GI Technology").  MTX and GI shall own jointly all patent 
rights, copyrights and know-how developed jointly by employees or consultants 
of MTX and GI (the "Joint Technology").  In the event that any solely 
developed technology of a Party includes Confidential Information of the 
other Party, the developing Party shall assign a one-half undivided interest 
in such technology to the other Party and such technology shall also 


                                     22

<PAGE>

constitute Joint Technology.  In addition, in the event that GI solely 
develops a chip assay for use on a hybridization platform, GI shall assign a 
one-half undivided interest in such technology to MTX and such technology 
shall also constitute Joint Technology.  Anything to the contrary 
notwithstanding, (a) MTX shall own all Chip Patent Rights used or developed 
in the Project and GI shall assign to MTX any interest GI may have in any 
Chip Patent Rights used or developed in the Project and any related know-how 
and (b) GI shall own all Gene Patent Rights arising out of or discovered 
through the use of the DNA Chip Products and MTX shall assign to GI any 
interest MTX may have in any Gene Patent Rights arising out of its 
involvement in the development of the DNA Chip Products or its involvement in 
the Project and any related know-how. MTX shall have the right at all times 
to use the MTX Technology and the Chip Patent Rights and GI shall have the 
right at all times to use the GI Technology and the Gene Patent Rights.

         4.2.  LICENSES.

         (a)  During the term of the Project, MTX shall grant and does hereby 
grant to GI and its designated Affiliates a royalty-free, worldwide, 
non-exclusive license under its Patent Rights and Copyrights and to use its 
Know-How, in each case, for the sole and exclusive purpose of GI's fulfilling 
its responsibilities under the Workplan and this Agreement.

         (b)  MTX shall grant and does hereby grant to GI and its designated 
Affiliates a royalty-free, worldwide, non-exclusive license under those Chip 
Patent Rights that are assigned to MTX by 


                                     23

<PAGE>

GI and to use the related know-how that is assigned to MTX by GI, in each 
case, for the purpose of conducting discovery research, including discovery 
research carried out on behalf of a third party.  Further, MTX shall and does 
hereby grant to GI and its designated Affiliates and Sublicensees a 
royalty-free, worldwide, non-exclusive license under those Chip Patent Rights 
that are assigned to MTX by GI and to use the related know-how that is 
assigned to MTX by GI for the purpose of conducting product development, 
process development and manufacturing.  The foregoing licenses shall be 
perpetual and shall survive any termination of this Agreement. Except as 
expressly set forth in this Section 4.2, there are no implied licenses from 
MTX to GI.  

         4.3.  RIGHTS OF MTX TO JOINT TECHNOLOGY OUTSIDE THE PROJECT. Subject 
to the provisions set forth in Sections 5.2-5.7 of this Agreement, MTX and 
its Affiliates shall have the right at all times to use the Joint Technology 
that does not encompass Gene Patent Rights in any and all of its other 
projects, provided that any DNA chip based technology which is developed in 
such other projects and which is reasonably useful or necessary or is 
required to develop, use, manufacture, distribute and/or sell DNA Chip 
Products is made available to GI under the terms of this Agreement.  Subject 
to the provisions set forth in Sections 5.2-5.7 of this Agreement and the 
royalty payment provisions set forth in Section 6.1 of this Agreement, MTX 
and its Affiliates shall have the right at all times to use the Joint 
Technology that does not encompass Gene Patent Rights in products sold to 
third parties other than GI.


                                     24

<PAGE>

         4.4.  RIGHTS OF GI TO JOINT TECHNOLOGY OUTSIDE THE PROJECT.  GI and 
its designated Affiliates shall have the right at all times to use the Joint 
Technology that does not encompass Chip Patent Rights (except for the limited 
right provided for in Section 4.2(b) of this Agreement) for discovery 
research, including discovery research carried out on behalf of a third 
party.  Further, GI and its designated Affiliates and Sublicensees shall have 
the right at all times to use the Joint Technology that does not encompass 
Chip Patent Rights (except for the limited right provided for in Section 
4.2(b) of this Agreement) for product development, process development and 
manufacturing purposes.

                             ARTICLE V.  EXCLUSIVITY

         5.1.  GENERAL RIGHTS.  Except as otherwise set forth in this Article 
V, MTX shall have the right to enter into collaborations with third parties 
other than GI (including, without limitation, Affiliates of MTX) and to sell 
products to third parties other than GI (including, without limitation, 
Affiliates of MTX).  

         5.2.  USE OF PROPRIETARY GENE SEQUENCES.  During the Exclusivity
Period, MTX agrees to comply with the provisions of Sections 5.3-5.7 of this
Agreement.  In addition, both during and subsequent to the Exclusivity Period,
MTX agrees not to (x) collaborate with a third party other than GI (including,
without limitation, Affiliates of MTX) on gene sequences that are Confidential
Information of GI or (y) supply a third party other than GI (including, without
limitation, Affiliates of MTX) with 


                                     25

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

products containing Probes for gene sequences that are Confidential 
Information of GI unless the other third party independently furnishes MTX 
with the gene sequences or the gene sequences become published or generally 
known to the public through no fault or omission on the part of MTX and its 
Affiliates.  Anything to the contrary notwithstanding, MTX shall have the 
right, at any time, to collaborate with a third party other than GI 
(including, without limitation, Affiliates of MTX) on Additional Gene 
Sequences that are Confidential Information of GI where the third party 
independently furnishes MTX with the Additional Gene Sequences.

         5.3.  USE OF PROBES.  MTX shall have the right at all times to
use the Probes in other projects and products, provided that the Probes are
selected and developed independent of the Project and MTX complies with the
provisions of Sections 5.2 and 5.4-5.7 of this Agreement.

         5.4.  GI EXCLUSIVITY ON COLLABORATIONS INVOLVING THE [     *     ] 
FIELD.  During the Exclusivity Period, MTX agrees not to enter into a 
collaboration with a third party other than GI (including, without 
limitation, Affiliates of MTX) for the purpose of developing and applying 
MTX's DNA Chip Technology to Gene Expression Screening in the [     *     ] 
Field unless all of the following conditions are met.

         (a)  The other third party independently furnishes MTX with the
gene sequences.

         (b)  The collaboration with the other third party involves gene 
sequences accounting for [     *     ] or less of the 

                                    26

<PAGE>


                        CONFIDENTIAL TREATMENT REQUESTED



gene sequences 
furnished by GI to MTX for the [     *     ]Field pursuant to Section 2.2 of 
this Agreement.

         (c)  The collaboration with the other third party involves Probes 
accounting for [     *     ] or less of the Probes contained in the DNA 
Chips developed for the [     *     ]Field.

         5.5.  GI EXCLUSIVITY ON COLLABORATIONS INVOLVING THE [     *     ].  
During the Exclusivity Period, MTX agrees not to enter into a collaboration 
with a third party other than GI (including, without limitation, Affiliates 
of MTX) for the purpose of developing and applying MTX's DNA Chip Technology 
to Gene Expression Screening involving the [     *     ] unless all of the 
following conditions are met.

         (a)  The other third party independently furnishes MTX with the
gene sequences.

         (b)  The collaboration with the other third party involves a 
gene sequence that is not publicly available and has not been furnished or 
identified by GI as part of the [     *     ] pursuant to Section 2.2 of this 
Agreement.

         (c)  MTX shall have used good faith efforts to effect a three-way
collaboration among MTX, GI and the other third party involving the gene
sequence prior to entering into the collaboration with the other third party.

         5.6  GI EXCLUSIVITY ON COLLABORATIONS INVOLVING THE GI NOVEL GENE 
DISCOVERY FIELD.  During the Exclusivity Period, MTX agrees not to enter into 
a collaboration with a third party other than GI (including, without 
limitation, Affiliates of MTX) for the purpose 


                                     27

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

of developing and applying MTX's DNA Chip Technology to Gene Expression 
Screening in the GI Novel Gene Discovery Field unless all of the following 
conditions are met.

         (a)  The other third party independently furnishes MTX with the gene 
sequences.

         (b)  The collaboration with the other third party involves a partial 
gene sequence that the other third party has identified as representative of 
a family of genes.

         (c)  MTX shall have identified such partial gene sequence to GI and 
GI shall have been given a [     *     ] period (triggered by written 
notification to GI from MTX of the identification of the GI partial gene 
sequence and the fact that it is representative of a family of genes) to 
identify specific genes encompassing such partial gene sequence.

         (d)  Any specific genes encompassing such partial gene sequence that 
are identified by GI during such [     *     ] period are excluded from the 
collaboration with the other third party.

         (e)  To the extent that GI is unable to identify specific genes 
encompassing such partial gene sequence within such thirty (30)-day period, 
GI shall have been afforded an additional fifteen (15)-day period to make a 
proposal to MTX with respect to a collaboration to identify such genes and 
MTX shall have considered in good faith any such proposal prior to entering 
into the collaboration with the other third party.


                                     28

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

         5.7.  LIMITATIONS ON PRODUCT SALES INVOLVING THE GENE FIELDS. During 
the Exclusivity Period, MTX agrees not to sell products (or any combination 
of products) that, despite whether or not such products are labelled for such 
purposes, could reasonably be anticipated to be used by third parties in a 
manner which would undermine the exclusivity provisions of Sections 5.4-5.6 
of this Agreement, whether such products are developed by MTX and/or its 
Affiliates or by MTX and/or its Affiliates in collaboration with a third 
party other than GI.

         5.8.  PROJECT REFUND AND PAYMENT ADJUSTMENT. In the event that MTX 
enters into a collaboration with a third party other than GI (including, 
without limitation, Affiliates of MTX) for the purpose of developing and 
applying MTX's DNA Chip Technology to Gene Expression Screening for any gene 
sequences or in any gene field (as permitted hereunder) prior to the 
expiration of the initial term of the Project, MTX shall refund to GI that 
percentage as is set forth below of all amounts previously paid by GI to MTX, 
as of such date, pursuant to Section 3.2 of this Agreement.  Further, GI's 
future payment obligations under Section 3.2 of this Agreement shall be 
reduced by that percentage as is set forth below.

         Contract Year in Which        Percentage          Percentage
          Collaboration Occurs           Refund             Reduction
         ----------------------        ----------          ----------
                 1                    [     *     ]       [     *     ]
                 2                    [     *     ]       [     *     ]
                 3                    [     *     ]       [     *     ]


         5.9.  BILATERAL COMMUNICATION.  GI acknowledges that in order to
effect the terms of Sections 5.4-5.6 of this Agreement, MTX may 


                                     29

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

be required to inform a third party other than GI (including, without 
limitation, Affiliates of MTX) of its inability to collaborate on certain 
common gene sequences because of its contractual obligations to GI.  MTX 
agrees that whenever it is required to make such a disclosure to another 
third party (including, without limitation, Affiliates of MTX), it shall make 
the most limited disclosure possible (i.e., it shall identify the common gene 
sequence but shall not furnish any information regarding the gene sequence 
itself and shall not identify GI as the other contractual party).  Further, 
MTX agrees to inform GI of the fact that it has been approached by another 
third party (but not the identity of the third party) (including, without 
limitation, Affiliates of MTX) and agrees to identify to GI the common gene 
sequences involved (but not any information regarding the gene sequence 
itself).

                      ARTICLE VI.  BENCHMARKS AND ROYALTIES

         6.1  ROYALTIES TO GI.    Until such time as GI shall have been paid 
an amount equal [     *     ] the difference between (a) the amount paid by 
GI to MTX pursuant to Section 3.2 of this Agreement and (b) the amount, if 
any, refunded by MTX to GI pursuant to Section 5.8 of this Agreement, MTX 
shall pay to GI earned royalties at a rate equal to [     *     ] on all Net 
Sales by MTX, its Affiliates and Sublicensees of DNA Chip Products and Other 
DNA Chip Products which fall within the definition of DNA Chip Products or 
Other DNA Chip Products by virtue of involving (i) a Valid Claim under the 
Patent 


                                     30

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

Rights constituting Joint Technology, (ii) Copyrights constituting Joint 
Technology and/or (iii) Know-How constituting Joint Technology.  
Notwithstanding the foregoing, royalties shall be paid on hybridization 
platforms and DNA chip readers solely if such products fall within the 
definition of DNA Chip Products or Other DNA Chip Products by virtue of 
involving a Valid Claim under the Patent Rights constituting Joint 
Technology.  Subject to the foregoing limitations, royalties on DNA Chip 
Products and Other DNA Chip Products involving (i) a Valid Claim under the 
Patent Rights constituting Joint Technology shall be payable on a 
country-by-country basis with respect to Net Sales for any country where the 
DNA Chip Products or Other DNA Chip Products are distributed or sold in which 
there is a Valid Claim under Patent Rights constituting Joint Technology and 
(ii) solely Copyrights constituting Joint Technology and/or Know-How 
constituting Joint Technology shall be payable on a country-by-country basis 
for a period of [     *     ] after the first sale in each such country of 
the relevant DNA Chip Product or Other DNA Chip Products.  At the request of 
MTX, GI agrees to consider in good faith a reduction in the foregoing 
[     *     ] earned royalty rate in exchange for a commensurate increase in 
the total amount of royalties to be paid GI pursuant to this Section 6.1 
which is reflective of the time value of money.


                                     31

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

         6.2.  BENCHMARKS TO MTX FOR NOVEL HUMAN THERAPEUTIC COMPOUNDS. 

         (a)  GI shall pay to MTX the following benchmark payments for each 
Novel Human Therapeutic Compound. 

               Benchmark                      Payment per Compound
               ---------                      --------------------

1.        [     *     ] in one of the             [     *     ]
          European Community, Japan or 
          the United States

2.        [     *     ] in one of the             [     *     ]
          European Community, Japan or 
          the United States

3.        Upon the first of CPMP approval         [     *     ]
          or recommendation for approval
          in the European Community, 
          Japanese approval or FDA 
          approval

Anything to the contrary notwithstanding, in the case of Novel Human 
Therapeutic Compounds discovered through the use of the DNA Chips developed 
for the Gene Fields, the foregoing benchmarks shall be payable solely with 
respect to novel genes and novel uses that are discovered during the 
Exclusivity Period. Anything to the contrary notwithstanding, in the case of 
Novel Human Therapeutic Compounds discovered through the use of a DNA Chip 
developed for the Additional Gene Sequences, the foregoing benchmarks shall 
be payable (i) solely with respect to novel genes and novel uses that are 
discovered within [     *     ] of the delivery of the relevant DNA Chip to 
GI and (ii) solely if, prior to the time of the discovery, MTX has not made, 
for comparable quantities and terms, the DNA Chips for the Additional Gene 
Sequences (if permitted hereunder) or Other DNA Chip Products generally 
available to third party commercial entities other than GI for the purpose of 
Gene 


                                     32

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

Expression Screening in exchange for lower (or no) benchmark payments.  
In the latter case, the lowest (or no) benchmark payments shall apply in lieu 
of those set forth in this Section 6.2.

         (b)  Until such time as GI shall no longer have any information to 
report to MTX, GI shall provide MTX with written reports summarizing the 
status of its use of the DNA Chip Products for discovery research on an 
annual basis on or before February 15 of each calendar year.  Such reports 
shall specify the number of potential Novel Human Therapeutic Compounds 
discovered by GI through such annual period and the development stage of such 
potential Novel Human Therapeutic Compounds at the end of such annual period. 
 Anything to the contrary notwithstanding, the foregoing reports shall apply 
solely to those Novel Human Therapeutic Compounds subject to the benchmark 
payment obligations set forth in this Section 6.2 and/or the royalty payment 
obligations set forth in Section 6.3 of this Agreement.

         6.3.  ROYALTIES TO MTX FOR NOVEL HUMAN THERAPEUTIC COMPOUNDS.

         (a)  GI shall pay to MTX earned royalties at a rate equal to 
[     *     ] on all Net Sales by GI, its Affiliates and Sublicensees of each 
Novel Human Therapeutic Compound.  Anything to the contrary notwithstanding, 
in the case of Novel Human Therapeutic Compounds that are discovered through 
the use of the DNA Chips developed for the Gene Fields, the foregoing earned 
royalties shall be payable solely with respect to novel genes and novel uses 
that are discovered during the Exclusivity Period.  Anything to the contrary 


                                     33

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

notwithstanding, in the case of Novel Human Therapeutic Compounds discovered 
through the use of a DNA Chip developed for the Additional Gene Sequences, 
the foregoing earned royalties shall be payable (i) solely with respect to 
novel genes and novel uses that are discovered within [     *     ] of the 
delivery of the relevant DNA Chip to GI and (ii) solely if, prior to the time 
of the discovery, MTX has not made, for comparable quantities and terms, the 
DNA Chips for the Additional Gene Sequences (if permitted hereunder) or Other 
DNA Chip Products generally available to third party commercial entities 
other than GI for the purpose of Gene Expression Screening in exchange for 
lower (or no) royalty payments.  In the latter case, the lowest (or no) 
royalty payments shall apply in lieu of the royalties set forth in this 
Section 6.3.  Royalties on Novel Human Therapeutic Compounds involving a 
Valid Claim under the Gene Patent Rights shall be payable on a 
country-by-country basis with respect to Net Sales for any country where the 
Novel Human Therapeutic Compounds are distributed or sold in which there is a 
Valid Claim under the Gene Patent Rights.  Royalties on Novel Human 
Therapeutic Compounds not involving a Valid Claim under the Gene Patent 
Rights shall be payable on a country-by-country basis for a period of 
[     *     ] after the first sale in each country of the relevant Novel 
Human Therapeutic Compound.

         (b)  In the event that GI believes that it, or any of its designated 
Affiliates or Sublicensees, must make payments (including, without 
limitation, royalties, option fees or license 


                                     34

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

fees) to one or more third parties to obtain a license or similar right in 
the absence of which the MTX Technology could not be legally used in 
connection with the research, development, use, manufacture, distribution 
and/or sale of Novel Human Therapeutic Compounds, it shall so notify MTX.  
MTX shall then have the following two options up until the time GI reasonably 
anticipates that the first such Novel Human Therapeutic Compound will 
[     *     ]or the equivalent thereof in any country.  First, MTX may permit 
GI and its designated Affiliates and Sublicensees to make such payments and 
to deduct from royalties payable to MTX on Net Sales of such Novel Human 
Therapeutic Compounds an amount equal to up to [     *     ] of such third 
party payments, provided that the total royalties otherwise due to MTX on Net 
Sales of such Novel Human Therapeutic Compounds in any calendar year shall 
not be reduced by more than [     *     ] as a result of such deduction.  To 
the extent that such third party payments exceed the deduction permitted 
under this paragraph (b), GI shall be permitted to carry such amount forward 
to subsequent calendar years.  The foregoing royalty deduction shall be 
calculated independent of the royalty deduction permitted under paragraph (c) 
below, provided that in no event shall the total royalties due to MTX on Net 
Sales of all Novel Human Therapeutic Compounds in any calendar year be 
reduced by more than [     *     ] as a result of deductions taken under this 
paragraph (b) and paragraph (c) below. Alternatively, MTX shall have the 
right to prohibit GI and its designated Affiliates and 


                                     35

<PAGE>

                     CONFIDENTIAL TREATMENT REQUESTED


Sublicensees from making such payments, provided that MTX agrees to defend GI 
and its designated Affiliates and Sublicensees, their agents, directors, 
officers and employees, at MTX's cost and expense, and to indemnify and hold 
harmless GI and its designated Affiliates and Sublicensees and, their agents, 
directors, officers and employees, from and against any and all losses, 
costs, damages, fees or expenses arising out of or in connection with claims 
brought by the foregoing third parties relating to the failure of GI and/or 
its Affiliates and Sublicensees to make such payments to such third parties.  
In the event that MTX desires to defend, indemnify and hold harmless GI and 
its designated Affiliates and Sublicensees, MTX shall be required to furnish 
GI with reasonable evidence of its financial ability to absorb such liability 
exposure.  If, at such time as GI shall reasonably anticipate that the first 
such Novel Human Therapeutic Compound will [     *     ] or the equivalent in 
any country, MTX shall not have reached a resolution with such third parties 
that is satisfactory to GI, GI shall have the right to make such payments and 
to take the foregoing deductions from royalties.

         (c)  If GI, or its designated Affiliates or Sublicensees, must
make payments (including, without limitation, royalties, option fees or license
fees) to one or more third parties to obtain a license or similar right for any
country where a Novel Human Therapeutic Compound is distributed or sold in which
there is not a Valid Claim under the Gene Patent Rights in the absence of which
GI or its designated Affiliates or Sublicensees could not legally 


                                     36

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


develop, use, manufacture, distribute and/or sell such Novel Human 
Therapeutic Compound, GI shall have the right to deduct from royalties 
payable to MTX on Net Sales of all such Novel Human Therapeutic Compounds an 
amount equal to up to [     *     ] of such third party payments, provided 
that the total royalties otherwise due to MTX on Net Sales of all such Novel 
Human Therapeutic Compounds in any calendar year shall not be reduced by more 
than [     *     ] as a result of such deduction.  To the extent that such 
third party payments exceed the deduction permitted under this paragraph (c), 
GI shall be permitted to carry such amount forward to subsequent calendar 
years.  The foregoing royalty deduction shall be calculated independent of 
the royalty deduction permitted under paragraph (b) above, provided that in 
no event shall the total royalties due to MTX on Net Sales of all Novel Human 
Therapeutic Compounds in any calendar year be reduced by more than 
[     *     ] as a result of deductions taken under paragraph (b) above and 
this paragraph (c).

         6.4.  REPORTS AND PAYMENT.  Each Party shall deliver to the other 
Party within sixty (60) days after the end of each calendar quarter a written 
report showing its computation of royalties due under this Agreement upon Net 
Sales by such Party, its Affiliates and Sublicensees during such calendar 
quarter.  All Net Sales shall be segmented in each such report according to 
sales by such Party, each Affiliate and each Sublicensee, as well as on a 
country-by-country basis, including the rates of exchange used to convert 
such royalties to United States Dollars from the currency 


                                     37

<PAGE>

in which such sales were made.  For the purposes hereof, the rates of 
exchange to be used for converting royalties hereunder to United States 
Dollars shall be those published for the purchase of United States Dollars in 
the East Coast Edition of the WALL STREET JOURNAL for the last business day 
of the calendar quarter for which payment is due.  Subject to the provisions 
of Sections 6.5 and 6.6 of this Agreement, simultaneously with the delivery 
of each such report, the paying Party shall tender payment in United States 
Dollars of all royalties shown to be due therein.

         6.5.  FOREIGN ROYALTIES.  Where royalties are due hereunder for 
sales of Products in a country where, by reason of currency regulations or 
taxes of any kind, it is impossible or illegal for such Party, any Affiliate 
or Sublicensee to transfer royalty payments to the other Party for Net Sales 
in that country, such royalties shall be deposited in whatever currency is 
allowable by the person or entity not able to make the transfer for the 
benefit or credit of the other Party in an accredited bank in that country 
that is reasonably acceptable to the other Party.

         6.6.  TAXES.  Any and all income or similar taxes imposed or levied 
on account of the receipt of royalties payable under this Agreement which are 
required to be withheld by a Party shall be paid by such Party, its 
Affiliates or Sublicensees on behalf of the other Party and shall be paid to 
the proper taxing authority.  Proof of payment shall be secured and sent to 
the other Party by such Party, its Affiliates or Sublicensees as evidence of 
such payment in such form as required by the tax authorities having 


                                     38

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


jurisdiction over such Party, its Affiliates or Sublicensees.  Such taxes 
shall be deducted from the royalty that would otherwise be remittable by the 
Party, its Affiliates or Sublicensees.

         6.7.  RECORDS.  Each Party shall keep, and shall require all 
Affiliates and Sublicensees to keep, for a period of at least two years, 
full, true and accurate books of accounts and other records containing all 
information and data which may be necessary to ascertain and verify the 
royalties payable hereunder.  During the term of this Agreement and for a 
period of two years following its termination, each Party shall have the 
right from time to time (not to exceed once during each calendar year) to 
inspect in confidence, or have an agent, accountant or other representative 
inspect in confidence, such books, records and supporting data.

                              ARTICLE VII.  SUPPLY

         7.1.  SUPPLY OF DNA CHIP PRODUCTS.  Until the fifth anniversary of 
the expiration of the term of the Project, MTX shall supply GI, its 
designated Affiliates and Sublicensees with one hundred percent (100%) of 
their requirements of DNA Chip Products.  GI and its designated Affiliates 
shall have the right to use the DNA Chip Products for [     *     ], 
including [     *     ] carried out on behalf of third parties.  Further, GI 
and its designated Affiliates and Sublicensees shall have the right to use 
the DNA Chip Products for [     *     ].  Except for transfers 


                                     39

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


contemplated by the foregoing sentence, GI shall have no right to resell the 
DNA Chip Products.  

         7.2.  SUPPLY PRICE FOR DNA CHIP PRODUCTS.  Until such time as MTX is 
generally offering to third party commercial entities the right to purchase 
DNA Chip Products (if permitted hereunder) or Other DNA Chip Products for the 
purpose of Gene Expression Screening, the supply price to GI for its 
requirements of DNA Chip Products shall be as follows.  In the event that MTX 
contracts for the manufacture of the DNA Chip Products, the price to GI shall 
not exceed [     *     ].  In the event that MTX itself 
manufactures the DNA Chip Products, the price to GI for DNA Chip Products 
purchased shall not exceed [     *     ].  At such time as MTX is generally 
offering to third party commercial entities the right to purchase DNA Chip 
Products (if permitted hereunder) or Other DNA Chip Products for the purpose 
of Gene Expression Screening, MTX shall supply GI with its requirements of 
DNA Chip Products at the lowest price charged for comparable quantities and 
terms by MTX to its other third party commercial end-users of DNA Chip 
Products (if permitted hereunder) or Other DNA Chip Products; provided, 
however, that the favored supply price provided for in this sentence shall 
not be available for purchases of DNA chip readers on behalf of GI's 
Affiliates that are not controlled by GI or on behalf of GI's Sublicensees.

         7.3.  FORECASTS AND ADEQUATE SUPPLY OF DNA CHIP PRODUCTS. Commencing 
with the first full contract quarter subsequent to the 


                                     40

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


delivery by MTX to GI of the first DNA chip reader, during the term of this 
Agreement, GI shall provide MTX with forecasts of its requirements of DNA 
Chip Products at least [     *     ] prior to each contract quarter or at 
such other intervals or upon such other advance notice as is determined by 
the Research Management Committee.  Further, in order to ensure an adequate 
supply of DNA Chip Products to GI, GI shall have the right to contract with 
MTX for dedicated equipment and manpower as is necessary to meet GI's supply 
needs on terms mutually agreed upon by the Parties.

         7.4.  SUPPLY OF OTHER DNA CHIP PRODUCTS.  If, at any time prior to 
the [     *     ] of the expiration of the term of the Project, MTX is 
generally offering to third party commercial entities the right to purchase 
Other DNA Chip Products for the purpose of Gene Expression Screening and GI 
desires to purchase such Other DNA Chip Products for the purpose of Gene 
Expression Screening, MTX shall sell such Other DNA Chip Products to GI at 
the lowest price charged for comparable quantities and terms by MTX to its 
other third party commercial end-users of such Other DNA Chip Products.

         7.5.  RECORDS.  MTX shall keep true and accurate records to 
substantiate the supply price charged to GI pursuant to this Article VII.  
Upon request from GI, MTX shall permit GI or its authorized representative to 
inspect such records in confidence in order to verify the supply price 
charged to GI.


                                     41

<PAGE>

         ARTICLE VIII.  PATENT PROSECUTION AND INFRINGEMENT RIGHTS

         8.1.  RESPONSIBILITY FOR PATENTING OF TECHNOLOGY.  

         (a)  Except as otherwise provided in this Agreement, MTX shall have 
the right to seek or continue to seek or maintain patent protection on any 
MTX Technology, Joint Technology that does not encompass Gene Patent Rights 
and Chip Patent Rights in any country.  If MTX elects not to seek or continue 
to seek or maintain patent protection on any such Joint Technology in any 
country, GI shall have the right, at its expense, to file, procure and 
maintain in such countries patents on such Joint Technology that does not 
encompass Chip Patent Rights.  MTX agrees to advise GI of all decisions taken 
this paragraph in a timely manner in order to allow GI to protect its rights 
under this paragraph. Except as otherwise provided in this Agreement, GI 
shall have the right to seek or continue to seek or maintain patent 
protection on any GI Technology and Gene Patent Rights in any country.  Each 
Party shall bear all costs incurred by it in exercising the foregoing rights.

         (b)  Each Party shall provide the other Party with copies of all 
substantive communications from all patent offices regarding applications or 
patents on any Joint Technology promptly after the receipt thereof.  Each 
Party shall provide the other Party with copies of all proposed substantive 
communications to such patent offices regarding applications or patents on 
any Joint Technology in sufficient time before the due date in order to 
enable the other Party an opportunity to comment on the content thereof.


                                     42

<PAGE>

         (c)  Each Party shall make available to the other Party or its 
authorized attorneys, agents or representatives, such of its employees whom 
the other Party in its reasonable judgment deems necessary in order to assist 
it in obtaining patent protection for the Joint Technology.  Each Party shall 
sign or use its best efforts to have signed all legal documents necessary to 
file and prosecute patent applications or to obtain or maintain patents at no 
cost to the other Party.

         8.2.  INFRINGEMENT.

         (a)  Each Party shall promptly report in writing to the other Party 
during the term of this Agreement any (i) known infringement or suspected 
infringement of any of the Patent Rights, (ii) known infringement or 
suspected infringement of any of the Copyrights, or (iii) unauthorized use or 
misappropriation of Know-How or Confidential Information by a third party of 
which it becomes aware, and shall provide the other Party with all available 
evidence supporting said infringement, suspected infringement or unauthorized 
use or misappropriation.

         (b)  Each Party shall have the right to initiate an infringement or 
other appropriate suit against any third party who at any time has infringed, 
or is suspected of infringing, any of such Party's solely owned Patent Rights 
or Copyrights or of using without proper authorization all or any portion of 
such Party's solely owned Know-How.  Except as provided in paragraph (d) 
below, MTX shall have the first right to initiate an infringement or other 
appropriate suit against any third party who at any time has 


                                     43

<PAGE>

infringed, or is suspected of infringing, any of the Patent Rights 
constituting Joint Technology that does not encompass Gene Patent Rights or 
Copyrights constituting Joint Technology or of using without proper 
authorization all or any portion of the Know-How constituting Joint 
Technology.  With respect to any suit involving such Joint Technology, MTX 
shall give GI sufficient advance notice of its intent to file said suit and 
the reasons therefor, and shall provide GI with an opportunity to make 
suggestions and comments regarding such suit.  MTX shall keep GI promptly 
informed, and shall from time to time consult with GI regarding the status of 
any such suit and shall provide GI with copies of all documents filed in, and 
all written communications relating to, such suit.  MTX shall have the right 
to initiate an infringement or other appropriate suit against any third party 
who at any time has infringed, or is suspected of infringing, any of the Chip 
Patent Rights and GI shall have the right to initiate an infringement or 
other appropriate suit against any third party who at any time has infringed, 
or is suspected of infringing, any of the Gene Patent Rights.

         (c)  MTX shall have the sole and exclusive right to select counsel 
for any suit involving the Joint Technology that does not encompass Gene 
Patent Rights referred to in paragraph (b) above and shall, except as 
provided below, pay all expenses of the suit, including without limitation 
attorneys' fees and court costs.  GI, in its sole discretion, may elect, 
within sixty (60) days after the commencement of such litigation, to 
contribute a fixed percentage 


                                     44

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


of up to [     *     ] of the costs incurred by MTX in connection with such 
litigation, including, without limitation, reimbursement of MTX's expenses 
hereunder.  If it so elects, any damages, royalties, settlement fees or other 
consideration received by MTX or any of its Affiliates for past infringement 
or misappropriation as a result of such litigation shall be shared by the 
Parties pro-rata based on their respective sharing of the costs of such 
litigation.  In the event that GI elects not to contribute to the costs of 
such litigation, MTX and/or its Affiliates shall be entitled to retain any 
damages, royalties, settlement fees or other consideration for past 
infringement or misappropriation resulting therefrom.  If necessary or 
desirable, GI shall join as a party to the suit but shall be under no 
obligation to participate except to the extent that such participation is 
required as the result of being a named party to the suit. GI shall offer 
reasonable assistance to MTX in connection therewith at no charge to MTX 
except for reimbursement of reasonable out-of-pocket expenses, including 
salaries of GI's personnel, incurred in rendering such assistance.  GI shall 
have the right to participate and be represented in any such suit by its own 
counsel at its own expense.  If MTX requires GI to join in such suit and GI 
has not elected to contribute to the costs of such suit, MTX shall indemnify 
and defend GI against any claims or damages arising out of the initiation of 
such suits or any claims for injunctive relief against such third party 
infringers. MTX shall not settle any such 


                                     45

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

suit involving rights of GI without obtaining the prior written consent of 
GI, which consent shall not be unreasonably withheld.

         (d)  In the event that MTX elects not to initiate an infringement
or other appropriate suit involving the Joint Technology pursuant to paragraph
(b) above, MTX shall promptly advise GI of its intent not to initiate such suit,
and GI shall have the right, at its expense, of initiating an infringement or
other appropriate suit against any third party who at any time has infringed, or
is suspected of infringing, any of the Patent Rights  constituting Joint
Technology that does not encompass Chip Patent Rights or Copyrights constituting
Joint Technology or of using without proper authorization all or any portion of
the Know-How constituting Joint Technology.  In exercising its rights pursuant
to this paragraph (d), GI shall have the sole and exclusive right to select
counsel and shall, except as provided below, pay all expenses of the suit
including without limitation attorneys' fees and court costs.  MTX in its sole
discretion, may elect, within sixty (60) days after the commencement of such
litigation, to contribute a fixed percentage of up to [     *     ] of the
costs incurred by GI in connection with such litigation, including, without
limitation, reimbursement of GI's expenses hereunder.  If it so elects, any
damages, royalties, settlement fees or other consideration received by GI or any
of its Affiliates for past infringement or misappropriation as a result of such
litigation shall be shared by the Parties pro-rata based on their respective
sharing of the costs of such litigation.  In the event that MTX 


                                     46

<PAGE>

elects not to contribute to the costs of such litigation, GI and/or its 
Affiliates shall be entitled to retain any damages, royalties, settlement 
fees or other consideration for past infringement or misappropriation 
resulting therefrom.  If necessary or desirable, MTX shall join as a party to 
the suit but shall be under no obligation to participate except to the extent 
that such participation is required as a result of being a named party to the 
suit.  At GI's request, MTX shall offer reasonable assistance to GI in 
connection therewith at no charge to GI except for reimbursement of 
reasonable out-of-pocket expenses, including salaries of MTX's personnel, 
incurred in rendering such assistance.  If GI requires MTX to join in such 
suit and MTX has not elected to contribute to the costs of such suit, GI 
shall indemnify and defend MTX against any claims or damages arising out of 
the initiation of such suits or any claims for injunctive relief against such 
third party infringers.  MTX shall have the right to participate and be 
represented in any such suit by its own counsel at its own expense.

         8.3.  CLAIMED INFRINGEMENT.

         (a)  In the event that a third party at any time provides written 
notice of a claim to, or brings an action, suit or proceeding against, either 
Party or any of their respective Affiliates or Sublicensees, claiming 
infringement of its patent rights or copyrights or unauthorized use or 
misappropriation of its know-how, based upon an assertion or claim arising 
out of the development, use, manufacture, distribution and/or sale of DNA 
Chip Products or Other DNA Chip Products, such Party shall promptly 


                                     47

<PAGE>

notify the other Party of the claim or the commencement of such action, suit 
or proceeding, enclosing a copy of the claim and/or all papers served.  Each 
Party agrees to make available to the other Party its advice and counsel 
regarding the technical merits of any such claim at no cost to the other 
Party.

         (b)  EXCEPT AS SET FORTH IN SECTION 6.3 OF THIS AGREEMENT, THE
FOREGOING STATES THE ENTIRE RESPONSIBILITY OF THE PARTIES IN THE CASE OF ANY
CLAIMED INFRINGEMENT OR VIOLATION OF ANY THIRD PARTY'S PATENT RIGHTS OR
COPYRIGHTS OR UNAUTHORIZED USE OR MISAPPROPRIATION OF ANY THIRD PARTY'S
KNOW-HOW.

                    ARTICLE IX.  CONFIDENTIAL INFORMATION

         9.1.  TREATMENT OF CONFIDENTIAL INFORMATION.  Each Party hereto 
shall maintain the Confidential Information of the other Party in confidence, 
and shall not disclose, divulge or otherwise communicate such Confidential 
Information to others, or use it for any purpose, except as permitted or 
contemplated by this Agreement or pursuant to, and in order to carry out, the 
terms and objectives of this Agreement, and hereby agrees to exercise every 
reasonable precaution to prevent and restrain the unauthorized disclosure of 
such Confidential Information by any of its directors, officers, employees, 
consultants, subcontractors, agents, Affiliates or Sublicensees.

         9.2.  RELEASE FROM RESTRICTIONS.  The provisions of Section 9.1 
shall not apply to any Confidential Information disclosed hereunder which:


                                     48

<PAGE>

         (a)  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

         (b)  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; or

         (c)  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 on the part of the receiving Party or its Affiliates; or

         (d)  is required to be disclosed by the receiving Party to comply 
with applicable laws, to defend or prosecute litigation 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.

         9.3.  PUBLICATIONS.  The following restrictions shall apply with
respect to the disclosure in scientific journals or publications by any Party or
any of its Affiliates or any employee or consultant of any Party or any of its
Affiliates of Confidential Information of the other Party relating to the
Project:

         (a)  a Party (the "publishing Party") shall provide the other Party 
with an advance copy of any proposed publication (which may 


                                     49

<PAGE>

be in draft form) and such other Party shall have a reasonable opportunity to 
recommend any changes it reasonably believes are necessary to preserve patent 
rights, copyrights or know-how belonging in whole or in part to MTX or GI, 
and the incorporation of such recommended changes shall not be unreasonably 
refused; and

         (b)  if such other Party informs the publishing Party, within thirty 
(30) days of receipt of an advance copy of a proposed publication, that such 
publication in its reasonable judgment could be expected to have a material 
adverse effect on any patent rights, copyrights or know-how belonging in 
whole or in part to MTX or GI, the publishing Party shall, to the extent 
permitted by its agreements with its employees and consultants, delay or 
prevent such publication as proposed.  In the case of inventions, the delay 
shall be sufficiently long to permit the timely preparation and filing of a 
patent application(s) or application(s) for a certificate of invention on the 
information involved.

                             ARTICLE X.  TERMINATION

         10.1.  TERM.  Unless earlier terminated in accordance with the 
provisions of this Article X, this Agreement shall remain in effect until the 
later of (a) the expiration of the royalty payment obligations set forth in 
Article VI of this Agreement or (b) the supply obligations set forth in 
Article VII of this Agreement.

         10.2.  TERMINATION DUE TO LACK OF FEASIBILITY.

         (a)  In the event that the Parties mutually determine that the 
Project is not feasible, this Agreement shall be terminated 


                                     50

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

immediately.  In any such event, MTX shall return to GI the portion of the 
[     *     ] advance provided for in Section 3.2 of this Agreement which 
would not otherwise have been paid to MTX were it not an advance and each 
Party shall retain ownership of its technology.

         (b)  In the event that MTX determines that the Project is not 
feasible but GI disagrees, MTX shall have the right to terminate this 
Agreement on thirty (30) days prior written notice to GI.  In any such event, 
MTX shall return to GI the portion of the [     *     ] advance provided for 
in Section 3.2 of this Agreement which would not otherwise have been paid to 
MTX were it not an advance and each Party shall retain ownership of its 
technology.  Furthermore, in the event that, prior to the second anniversary 
of such termination, MTX shall desire to enter into a collaboration relating 
to the development and application of MTX's DNA Chip Technology to Gene 
Expression Screening with a third party other than GI (including, without 
limitation, Affiliates of MTX) possessing technology or know-how that would 
render the Project technologically feasible, MTX shall use good faith efforts 
to effect a three-way collaboration among MTX, GI and the other third party 
to complete the Project.  In the event that MTX is unable to effect a 
three-way collaboration but enters into the collaboration with the other 
third party, MTX shall refund to GI that percentage as is set forth below of 
all amounts previously paid by GI to MTX pursuant to Section 3.2 of this 
Agreement.


                                     51

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED


                         Contract Year
                           In Which                     Percentage
                      Termination Occurs                  Refund  
                      ------------------                ----------

                              1                        [     *     ]
                              2                        [     *     ]
                              3                        [     *     ]

The foregoing refund shall not be paid if GI shall have previously received a
refund pursuant to Section 5.8 of this Agreement.

         (c)  In the event that GI determines that the Project is not 
feasible but MTX disagrees, GI shall have the right to terminate this 
Agreement on thirty (30) days prior written notice to MTX.  In any such 
event, MTX shall be entitled to retain the [     *     ] advance provided for 
in Section 3.2 of this Agreement and each Party shall retain ownership of its 
technology.  

         10.3.  TERMINATION DUE TO LACK OF PROGRESS.  In the event that Goals 
A and B set forth in SCHEDULE A are not achieved by the end of the first 
Contract Year, GI shall have the right to terminate this Agreement on thirty 
(30) days prior written notice to MTX.  In any such event, MTX shall return 
to GI the portion of the [     *     ] advance provided for in Section 3.2 of 
this Agreement which would not have otherwise been paid to MTX were it not an 
advance and each Party shall retain ownership of its technology.

         10.4.  TERMINATION DUE TO AN IMPASSE.  In the event that the
Research Management Committee is unable to reach a decision by majority vote
with respect to any matter and such inability continues for a period of sixty
(60) days after the date on which the matter is first submitted to the Research
Management Committee, each Party shall have the right to refer the matter to the
chief 


                                     52

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED

operating officers of MTX and GI for resolution.  Except for an impasse 
relating to the feasibility of the Project (which shall be dealt with as 
specified in Section 10.2 of this Agreement), in the event of an impasse that 
(a) occurs prior to a commercially useful stage of development of the Project 
and (b) cannot be resolved by the chief operating officers of MTX and GI 
within thirty (30) days after the date on which the matter is first referred 
to them, each of MTX and GI shall have the right to terminate this Agreement 
on thirty (30) days prior written notice to the other Party.  In any such 
event, each Party shall retain ownership of its technology.  In the event 
that MTX is the terminating Party, it shall return to GI that portion of the 
[     *     ] advance provided for in Section 3.2 of this Agreement which 
would not otherwise have been paid to MTX were it not an advance.  
Furthermore, in the event that, prior to the second anniversary of such 
termination, MTX shall enter into a collaboration relating to the development 
and application of MTX's DNA Chip Technology to Gene Expression Screening 
with a third party other than GI (including, without limitation, Affiliates 
of MTX other than Affymax N.V., Affymax Technologies N.V. and Affymax 
Research Institute), MTX shall refund to GI that percentage as is set forth 
below of all amounts previously paid by GI to MTX pursuant to Section 3.2 of 
this Agreement.

                 Contract Year
                   In Which                 Percentage
               Termination Occurs             Refund  
               ------------------           ----------

                      1                    [     *     ]
                      2                    [     *     ]
                      3                    [     *     ]


                                     53

<PAGE>

The foregoing refund shall not be paid if GI shall have previously received a 
refund pursuant to Section 5.8 of this Agreement. In the event of an impasse 
that (a) occurs subsequent to a commercially useful stage of development of 
the Project and (b) cannot be resolved by the chief operating officers of MTX 
and GI within thirty (30) days after the date on which the matter is first 
referred to them, each of MTX and GI shall have the right to terminate the 
continuing work being conducted pursuant to the Project but not this 
Agreement.  In any such event, each Party shall retain ownership of its 
technology.

         10.5.  TERMINATION OF AGREEMENT FOR BREACH.  Each Party shall be
entitled (but not required) to terminate this Agreement and the licenses granted
hereunder to the other Party by written notice to the other Party in the event
that the other Party shall be in default of any of its material obligations
hereunder, and shall fail to remedy any such default within sixty (60) days
after notice thereof by the non-breaching Party.  Any such notice shall
specifically state that the non-breaching Party intends to terminate this
Agreement in the event that the breaching Party shall fail to remedy the
default.

         10.6.  SURVIVAL OF OBLIGATIONS; RETURN OF CONFIDENTIAL
INFORMATION.  Upon any termination of this Agreement, neither Party shall be
relieved of any obligations incurred prior to such termination.  Upon any
termination of this Agreement pursuant to Sections 10.2, 10.3 or 10.4 of this
Agreement, (a) the provisions of Sections 6.1, 6.4, 6.5, 6.6 and 6.7 of this
Agreement shall 


                                     54

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED


survive with respect to any Joint Technology that may have reached a 
commercially useful stage of development except that any refund made in 
accordance with either Section 10.2 or 10.4 shall be included in the amount 
deducted pursuant to Section 6.1(b) of this Agreement and (b) the provisions 
of Sections 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 7.1 and 7.2 shall survive with 
respect to any DNA Chip Products that may have been developed in the Project. 
 Upon any termination of this Agreement, the rights of GI to use the DNA Chip 
Products set forth in Section 7.1 of this Agreement shall survive with 
respect to those DNA Chip Products purchased by GI prior to such termination, 
subject to the continuing obligation to pay benchmarks and royalties to MTX 
pursuant to Sections 6.2, 6.3, 6.4, 6.5, 6.6 and 6.7 of this Agreement.  
Notwithstanding any termination of this Agreement, the obligations of the 
Parties under Article IX and Sections 6.3(b), 8.3 and 11.1, as well as under 
any other provisions which by their nature are intended to survive any such 
termination, shall survive and continue to be enforceable.  Upon any 
termination of this Agreement, each Party shall promptly return to the other 
Party all written Confidential Information, and all copies thereof, of the 
other Party which is not covered by a license surviving such termination.

             ARTICLE XI.  INDEMNIFICATION AND LIABILITY LIMITATIONS

         11.1.  PRODUCT LIABILITY INDEMNIFICATION

         [     *     ]


                                     55

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED


         [     *     ]


                                     56

<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED


         [     *     ]

         11.2.  LIABILITY.  [     *     ]


                                     57

<PAGE>

                               ARTICLE XII. EXPORT

         12.1.  ACKNOWLEDGMENT.  The Parties acknowledge that the export of 
technical data, materials or products is subject to the exporting Party 
receiving the necessary export licenses and that the Parties cannot be 
responsible for any delays attributable to export controls which are beyond 
the reasonable control of either Party.  The Parties agree that regardless of 
any disclosure made by the Party receiving an export of an ultimate 
destination of any technical data, materials or products, the receiving Party 
will not reexport either directly or indirectly, any technical data, material 
or products without first obtaining the applicable validated or general 
license from the United States Department of Commerce, United States Food and 
Drug Administration and/or any other agency or department of the United 
States Government, as required. The receiving Party shall provide the 
exporting Party with any information, materials, certifications or other 
documents which may be reasonably required in connection with such exports 
under the Export Administration Act of 1979, as amended, its rules and 
regulations, the Federal Food, Drug and Cosmetic Act and other applicable 
export laws.

         12.2.  WRITTEN ASSURANCE.  Without limitation of the foregoing, and 
in support of maintaining a general license for the export of technical data 
under this Agreement, a Party receiving an export agrees to not knowingly 
export or reexport any technical data or materials furnished to such Party 
under this Agreement, any part thereof or any direct product thereof, 
directly or indirectly, 


                                     58

<PAGE>

without first obtaining permission to do so from the United States Department 
of Commerce, the United States Food and Drug Administration and/or other 
appropriate United States governmental agencies, into Afghanistan, the 
People's Republic of China, South Africa, Namibia or any of those countries 
listed from time to time in supplements to Part 370 to Title 15 of the Code 
of Federal Regulations in Country Groups Q, S, Y or Z, which, as of the date 
of this Agreement, are as follows:  Group Q (Romania), Group S (Libya), Group 
Y (Albania, Armenia, Azerbijan, Belarus, Bulgaria, Cambodia, Estonia, 
Georgia, Kazakhstan, Kyrgyzstan, Laos, Latvia, Lithuania, Mongolia, Russia, 
Tajikistan, Turkmenistan, Ukraine, Uzbekistan and Vietnam) and Group Z (Cuba 
and North Korea).

                          ARTICLE XIII.  MISCELLANEOUS

         13.1.  REPRESENTATIONS AND WARRANTIES OF MTX.  MTX represents and 
warrants to GI that (1) it has the full right and authority to enter into and 
perform this Agreement, (2) it has the right or has obtained the necessary 
consents, waivers, approvals or other authorizations to make the assignments 
provided for in Section 4.1 of this Agreement and to grant the licenses and 
rights set forth in Sections 4.2, 7.1, 8.1 and 8.2 of this Agreement and (3) 
it has obtained from Affymax N.V. and its affiliated entities (the "Affymax 
Entities") any and all consents, waivers, approvals or other authorizations 
necessary to enter into and perform this Agreement without violating the 
terms of its agreements with the Affymax Entities.  MTX hereby agrees to 
indemnify, defend, protect 


                                     59

<PAGE>

and hold harmless GI and its Affiliates and Sublicensees against any and all 
losses, costs, damages, expenses, fees and/or liabilities directly or 
indirectly resulting from any claims, lawsuits and/or judgments ("Claims") to 
the extent that such Claims are based on allegations predicated on the 
foregoing representations and warranties being false.

         13.2.  PUBLICITY.  Neither Party, nor any of its Affiliates, shall 
originate any publicity, news release or other public announcement, written 
or oral, relating to this Agreement or the existence of an arrangement 
between the Parties, without the prior written approval of the other Party, 
which approval shall not be unreasonably withheld, except as otherwise 
required by law.

         13.3.  ASSIGNMENT.  Except as otherwise provided in this Agreement, 
neither this Agreement nor any of the rights or obligations hereunder may be 
assigned by either Party without the prior written consent of the other 
Party, except to a party who acquires all or substantially all of the 
business of the assigning Party by merger, sale of assets or otherwise.

         13.4.  GOVERNING LAW.  This Agreement shall be governed by and 
interpreted in accordance with the laws of the Commonwealth of Massachusetts.

         13.5.  FORCE MAJEURE.  In the event that either Party is prevented 
from performing or is unable to perform any of its obligations under this 
Agreement due to any act of God; fire; casualty; flood; war; strike; lockout; 
failure of public utilities; injunction or any act, exercise, assertion or 
requirement of 


                                     60

<PAGE>

governmental authority; epidemic; destruction of production facilities; 
riots; insurrection; inability to procure or use materials, labor, equipment, 
transportation or energy; or any other cause beyond the reasonable control of 
the Party invoking this Section 13.5 if such Party shall have used its best 
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 such occurrence.

         13.6.  WAIVER.  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.

         13.7.  NOTICES.  Any notice or other communication in connection 
with this Agreement must be in writing and if by mail, by certified mail, 
return receipt requested, and shall be effective when delivered to the 
addressee at the address listed below or such other address as the addressee 
shall have specified in a notice actually received by the addressor.

                If to MTX:

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


                                     61

<PAGE>

                If to GI:

                             Genetics Institute, Inc.
                             87 CambridgePark Drive 
                             Cambridge, Massachusetts 02140 
                             Attention:  President


        13.8.  NO AGENCY.  Nothing herein shall be deemed to constitute 
either Party as the agent or representative of the other Party, or both 
Parties as joint venturers or partners for any purpose.  Each Party shall be 
an independent contractor, not an employee or partner of the other Party, and 
the manner in which a Party renders its services under this Agreement shall 
be within such Party's sole discretion.  Neither Party shall be responsible 
for the acts or omissions of the other Party, and neither Party will have 
authority to speak for, represent or obligate the other Party in any way 
without prior written authority from the other Party.

        13.9.  ENTIRE AGREEMENT.  This Agreement and the Schedules hereto 
(which Schedules are deemed to be a part of this Agreement for all purposes) 
contain the full understanding of the Parties with respect to the subject 
matter hereof and supersede all prior understandings and writings relating 
thereto.  No waiver, alteration or modification of any of the provisions 
hereof shall be binding unless made in writing and signed by the Parties by 
their respective officers thereunto duly authorized.

        13.10.  HEADINGS.  The headings contained in this Agreement are for 
convenience of reference only and shall not be considered in construing this 
Agreement.


                                     62

<PAGE>

        13.11.  SEVERABILITY.  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 provisions held to be 
unenforceable.

        13.12.  SUCCESSORS AND ASSIGNS.  This Agreement shall be binding upon 
and inure to the benefit of the Parties hereto and their successors and 
permitted assigns.

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

        13.14.  COUNTERPARTS.  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.

        IN WITNESS WHEREOF, the Parties hereto have caused this Agreement to 
be executed as a sealed instrument in their names by 

                                     63

<PAGE>

their properly and duly authorized officers or representatives as of the date
first above written.

                                             AFFYMETRIX, INC.



                                             By: /s/ Stephen P. A. Fodor
                                                ------------------------
                                                Stephen P. A. Fodor,
                                                President and Chief
                                                Technical Officer



                                             By: /s/ David B. Singer
                                                ------------------------
                                                David B. Singer,
                                                President and Chief Executive 
                                                Officer



                                             GENETICS INSTITUTE, INC.



                                             By: /s/ 
                                                ------------------------
                                                Vice President, Corporate
                                                Development


                                       64
<PAGE>

                        CONFIDENTIAL TREATMENT REQUESTED


                                   SCHEDULE A

GOALS FOR YEAR 01 OF THE COLLABORATION:

[     *     ]

WORKPLAN FOR YEAR 01 OF THE COLLABORATION:

[     *     ]

WORKPLAN YEAR 01:

[     *     ]

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


[     *     ]


<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


[     *     ]


<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


[     *     ]

MILESTONES (These are to be completed during the course of the entire 
collaboration)

[     *     ]


MILESTONE:                                                  PERFORMANCE BONUS

1. TECHNICAL ACHIEVEMENTS:

[     *     ]


<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


[     *     ]


<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


                                   SCHEDULE B

                                  [     *     ]

     Members of the [     *     ] are those containing the following 
[     *     ] which reflects the [     *     ]:

     [     *     ]


<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


                                   SCHEDULE C

                            CONTRACT YEAR L BUDGET


GI Funding of [     *     ] FTEs                               $[     *     ]
GI Capital Equipment Funding                                   $[     *     ]
                                                                -------------

                                               TOTAL           $[     *     ]
                                                                   

<PAGE>

                            CONFIDENTIAL TREATMENT REQUESTED BY AFFYMETRIX, INC.





                                SUPPLY AGREEMENT

                                Affymetrix, Inc. 
                                       and
                            Genetics Institute, Inc.








<PAGE>

                                SUPPLY AGREEMENT

Contents
                                                                Page
                                                                ----

1.   Introduction                                                 3
2.   Definitions                                                  3
3.   Probe Array Supply                                           8
4.   Exclusivity                                                 13
5.   Consulting                                                  14
6.   Compensation                                                14
7.   Fees and Royalties                                          16
8.   Intellectual Property                                       18
9.   Confidentiality                                             19
10.  Warranty                                                    20
11.  Indemnity                                                   21
12.  Term and Termination                                        22
13.  Miscellaneous                                               22




                                        2
<PAGE>

This supply agreement ("Agreement") is effective as of December 8, 1995
("Effective Date") between Affymetrix, Inc. ("AMTX") a California corporation
having its principal place of business at 3380 Central Expressway, Santa Clara,
California 95051, and Genetics Institute, Inc. ("GI") a Delaware corporation
having its principal place of business at 87 CambridgePark Drive, Cambridge,
Massachusetts 02140.  


1    INTRODUCTION

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

1.2  GI has research and development capabilities, and facilities to conduct
     research and development activities in the area of biotechnology and the
     application thereof to the development, production, and manufacture,
     registration, and marketing of biotechnolgy based pharmaceutical products.

1.3  AMTX and GI have entered into a Development and Supply Agreement effective
     November 15, 1994 (the "Collaboration Agreement") for the collaborative
     development of DNA probe array based technology.

1.4  AMTX and GI desire to enter into an agreement whereby AMTX will supply GI
     with DNA probe arrays for research and development activities to support
     additional activities to measure gene expression in order to discover novel
     therapeutic compounds. 

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

2    DEFINITIONS

2.1  "Affiliate" shall mean any corporation, company, partnership, joint venture
     and/or firm which controls, is controlled by, or is under common control
     with a Party.  For purposes of this Section, "control" shall mean, in the
     case of corporations (or foreign equivalents of corporations), direct or
     indirect ownership of at least 50% of the 


                                        3
<PAGE>

     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.  Except for Article 9 of this Agreement, for purposes of this
     definition, Affiliates of GI shall not include American Home Products
     Corporation, a Delaware corporation.

2.2  "AMTX Confirmation" shall have the meaning in Section 3.3 below.

2.3  "Collaborators" shall mean the third party(ies) that participate with GI in
     a GI Collaboration.

2.4  "Confidential Information" shall mean all information and materials,
     patentable or otherwise, of a Party which are disclosed and designated as
     confidential 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, methodologies, equipment, data, reports, know-how, preclinical
     and clinical trials and the results thereof, sources of supply, patent
     positioning, business plans, and the terms of this Agreement, including any
     negative developments.  For purposes of clarification, in the event that
     all of a Target Sequence becomes publicly known, but a scientific rationale
     for the selection of a particular combination of genes identified by GI is
     not publicly known, such particular combination of genes shall still be
     considered Confidential Information of GI. Confidential Information shall
     also include the scientific rationale for GI's selection of a particular
     combination of genes and GI's intended application of the Probe Arrays
     directed to a particular combination of genes.

2.5  "Custom Chip Project" shall refer to the design and manufacture of at least
     one Lot of Probe Arrays for a particular Target Sequence, as specified by
     GI pursuant to this Agreement.

2.6  "Fabrication Verification Criteria" shall mean the fabrication verification
     criteria set forth in Exhibit B.

2.7  "GI's Area Of Interest" shall mean the use of Probe Arrays as a research
     tool to measure the presence and/or levels of expressed nucleic acid
     sequences for the purpose of discovering Novel Therapeutic Compounds which,
     in each case, are encoded by or regulated by the genes (or their
     interspecies homologues) probed for on a Probe Array or are gene products
     identified by the elimination of proteins encoded by the nucleic acid
     sequences on a Probe Array.  GI's Area Of Interest shall expressly exclude
     the use of Probe Arrays (but not Novel Therapeutic Compounds) in clinical
     diagnosis of disease or forensic applications, human or 


                                        4
<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


otherwise.

2.8  "GI Collaboration" shall mean a bona fide scientific collaboration in GI's
     Area Of Interest, between GI or any of its Affiliates and a third party, in
     which such third party receives the biological materials and/or proprietary
     information of GI and/or its Affiliates, or in which GI and/or its
     Affiliates obtains the biological materials and/or proprietary information
     of a third party.  GI Collaboration shall not include business
     relationships based, in significant part, on a contract in which GI
     provides contract services for a third party involving use of the Probe
     Arrays on a fee-for-service or similar basis.

2.9  "High Complexity Probe Arrays" shall mean Probe Arrays containing more than
     [  *  ] probes and no more than [  *  ] probes of varying lengths, such
     probes encoding sequences representing no more than [         *        ]
     different genes.

2.10 "High Complexity Trigger Date" shall mean the date on which AMTX
     demonstrates the performance of High Complexity Probe Arrays in accordance
     with the criteria established by the Parties pursuant to this Agreement.

2.11 "Lot" shall refer to [*] Probe Arrays directed to a particular Target
     Sequence.   

2.12 "Low Complexity Probe Arrays" shall mean Probe Arrays containing no more
     than [  * ] probes of varying lengths, such probes encoding sequences
     representing no more than [*] different genes.

2.13 "Low Complexity Trigger Date" shall mean the date on which AMTX
     demonstrates the performance of Low Complexity Probe Arrays in accordance
     with the conditions in Exhibit A.

2.14 "Net Sales" shall mean the aggregate United States Dollar equivalent of
      [                                                                        
                                *                                              
                    ] less a)[                                                 
                                                                               
                                                                               
                    *                                                          
                                                                               
                                                                               
          ]



                                        5
<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


[                                                                              
                  *                                                            
                                                                               
         ]  Net Sales shall not include [           *                          
                                                              ]  If GI, an
Affiliate, Collaborator, licensee, or sublicensee sells Novel Therapeutic
Compounds to or through a distributor (which is not an Affiliate, Collaborator,
licensee, or sublicensee of GI), Net Sales shall be [                          
                                                     *                         
                                                                 ] In the event
that GI or any of its Affiliates, Collaborators, licensees, or sublicensees
shall make any transfer of Novel Therapeutic Compounds to third parties for
other than monetary value in whole or in part, such transfer shall be considered
a sale hereunder for accounting and royalty purposes. Net Sales for any such
transfers shall be determined on a country-by-country basis and shall be [     
                                                                               
                                                                               
                             *                                                 
                                                                               
                                                                               
                                                                        ] 
Notwithstanding the foregoing, no transfer of Novel Therapeutic Compounds for
test or developmental purposes or as samples shall be considered a sale
hereunder for accounting and royalty purposes unless such transfer is for
monetary value.  If Novel Therapeutic Compounds are sold as part of a system,
package, or combination product, Net Sales shall be [                          
                                                                               
                                         *                                     
                                               ]. If the Novel Therapeutic
Compound is not sold separately, [                                             
                                     *                                         
                                 ].

2.15 "Novel Therapeutic Compound" shall mean a compound that is, or is derived
     from, a Novel Gene Therapeutic or a Novel Use Therapeutic. For purposes of
     the definition,  if a Probe 

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


     Array was useful to GI, or its Affiliates or Collaborators in the 
     discovery of the Novel Gene Therapeutic or Novel Use Therapeutic, the 
     Novel Gene Therapeutic or Novel Use Therapeutic shall be deemed to have 
     been discovered through the use of  Probe Arrays.  Novel Therapeutic 
     Compounds shall not include [                              *
                                  ] using genes which are discovered, or 
     genes for which uses are discovered, by GI, its Collaborators or 
     Affiliates through use of Probe Arrays.  Novel Therapeutic Compounds 
     shall include such [                       *
             ] utilizes Probe Arrays.
     
2.16 "Novel Gene Therapeutics" shall mean a therapeutic protein (or any peptide
     or domain deleted, modified (e.g., by chemical or enzymatic cleavage or
     otherwise), variant, or mutant form thereof) expressed by a gene discovered
     by GI, or its Affiliates or Collaborators,  through the use of Probe
     Arrays.

2.17 "Novel Use Therapeutics" shall mean a therapeutic protein (or any peptide
     or domain deleted, modified (e.g., by chemical or enzymatic cleavage or
     otherwise), variant, or mutant form thereof) whose use is discovered by GI,
     or its Affiliates or Collaborators through the use of Probe Arrays. 

2.18 "Optimization Probe Arrays" shall mean a sample set of [  *  ] Probe
     Arrays to be produced by AMTX after Sample Delivery for a Target Sequence
     in the event that GI requests that a probe set be revised after Sample
     Delivery for a particular Custom Chip Project.

2.19 "Party" shall mean AMTX or GI.  "Parties" shall mean AMTX and GI.

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

2.21 "Project Term" shall mean the period commencing on the Low Complexity
     Trigger Date and ending on the first anniversary of the High Complexity
     Trigger Date, but in no event shall be a period of less than two (2) years.
     In the event that the High Complexity Trigger Date does not occur before
     [       *      ], the Project Term shall end on January 1, 1999.  The 
     Project Term may be extended  upon mutual written consent of the Parties.

2.22 "Reserved Production Capacity" shall mean the ability of AMTX to fabricate
     [ * ] Probe Arrays pursuant to this Agreement in [ * ] business days.

                                       7

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


2.23 "Resupply Term" shall mean, for a particular Custom Chip Project, eighteen
     (18) months  from the date GI last orders a Lot of Probe Arrays for such
     particular Custom Chip Project, but in no event later than the later of (1)
     January 1, 2001, or (2) four (4) years from the High Complexity Trigger
     Date.  The Resupply Term may be extended upon mutual written agreement of
     the Parties.

2.24 "Sample Delivery" shall have the meaning in Section 3.3.1 below.

2.25 "Target Sequence" shall mean the set of sequences specified by GI to AMTX
     for which GI desires to have AMTX perform a particular Custom Chip Project.

2.26 "Patent Claim" shall mean a claim of an unexpired patent owned or
     controlled by GI or  its Collaborators or Affiliates which shall not have
     been withdrawn, canceled or disclaimed, nor held invalid or unenforceable
     by a court of competent jurisdiction in an unappealed or unappealable
     decision, or the claim of a patent application which has not been on file
     for more than five (5) years.

3    PROBE ARRAY SUPPLY

3.1  During the Project Term, GI will identify at least [   *   ] but no more
     than [    *     ] different Custom Chip Projects.  No fewer than [   *   ]
     Custom Chip Projects will be identified by GI in the twelve (12) month
     period beginning on the Low Complexity Trigger Date and no fewer than [  *
        ] Custom Chip Projects will be identified by GI in the twelve (12) month
     period beginning on the High Complexity Trigger Date.  Of such Custom Chip
     Projects, no more than [   *   ] will be for Low Complexity Probe Arrays. 
     AMTX will not be obligated to provide GI with High Complexity Probe Arrays
     until [      *      ], but if the manufacture of such High Complexity Probe
     Arrays is considered, in AMTX' reasonable opinion, to be technically and
     commercially feasible, GI may request AMTX to manufacture and AMTX may
     agree to manufacture High Complexity Probe Arrays before [      *       ]. 
     AMTX will be obligated to produce and supply to GI Probe Arrays for all
     Target Sequences identified to AMTX before the end of the Project Term.

3.1.1     GI will supply the necessary genes for testing probe arrays according
          to Exhibit A by December 11, 1995.  AMTX will perform experiments to
          demonstrate the performance of 

                                       8

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


          Low Complexity Probe Arrays pursuant to Exhibit A.  Upon such 
          demonstration of the performance of the Low Complexity Probe 
          Arrays,  AMTX will provide notice in writing to GI, along with a 
          description of the experiments performed to demonstrate such 
          performance.  In the event that AMTX has not demonstrated, to GI's 
          reasonable satisfaction, the performance of Low Complexity Probe 
          Arrays, pursuant to Exhibit A by [    *    ], GI may, at its 
          option, terminate this Agreement or agree to extend the foregoing 
          deadline by an agreed upon amount of time needed to demonstrate 
          performance of the Low Complexity Probe Arrays pursuant to 
          Exhibit A.

3.1.2     AMTX will perform experiments to demonstrate the performance of High
          Complexity Probe Arrays by [      *       ].  The Parties shall
          mutually determine and agree upon performance criteria for High
          Complexity Probe Arrays, based upon the performance criteria in
          Exhibit A.  Upon such demonstration of the performance of the High
          Complexity Probe Arrays, AMTX will provide notice in writing to GI,
          along with a description of the experiments performed to demonstrate
          such performance.  In the event that AMTX has not demonstrated, to
          GI's reasonable satisfaction, the performance of High Complexity Probe
          Arrays by [       *       ], GI may, at its option, elect not to
          identify any additional Custom Chip Projects, or agree to extend the
          foregoing deadline by an agreed upon amount of time.  In the event
          that GI elects not to identify any additional Custom Chip Projects,
          the minimum order requirements set forth in the first sentence of
          Section 3.1 shall be waived.  In the event that GI agrees to extend
          the foregoing deadline, the limit on the number of Low Complexity
          Probe Arrays set forth in Section 3.1 shall be waived, it being
          understood that GI shall be permitted, but not obligated, to identify
          additional Custom Chip Projects that are Low Complexity Probe Arrays
          (i.e., in addition to the minimum requirement of [ * ]) prior to two
          (2) years from the Low Complexity Trigger Date, to a maximum of [  *
              ] such Custom Chip Projects.  In addition to the foregoing
          alternatives, GI shall have the right to continue to identify Custom
          Chip Projects, with the understanding that the High Complexity Trigger
          Date is not scientifically attainable.  In such circumstance, the
          limit on the number of Low Complexity Probe Arrays set forth in
          Section 3.1 shall be increased to up to [    *    ], and the limit on
          the number of genes set forth in Section 2.12 shall be increased to up
          to, if 

                                       9

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


          technically feasible, [        *        ].  In the event that the 
          sequences representing more than  [ * ] genes are placed on Low 
          Complexity Probe Arrays pursuant to this Section, the price of 
          Custom Chip Projects for such Low Complexity Probe Arrays set forth 
          in Section 6.1 (but not the maximums set forth in Section 7.1) 
          shall be increased in proportion to the number of genes represented 
          on such Probe Arrays, up to the price of Custom Chip Projects for 
          High Complexity Probe Arrays set forth in Section 6.1.

3.2  GI will identify the Target Sequence for a Custom Chip Project to AMTX by
     delivering to AMTX: 1) a diskette identifying the Target Sequence in a
     format mutually agreed upon by the Parties, and 2) an identification of the
     expected number of probes to be formed on a Probe Array directed to the
     Target Sequence, and 3) an identification of the probe lengths and number
     of probes in a Probe Array desired by GI for the particular sequences
     comprising the Target Sequence (not to exceed [    *    ] base probes
     without the consent of AMTX), and 4) a good faith estimate of the number of
     Lots of Probe Arrays needed by GI for the Target Sequence and the expected
     timing for production of such Lots, and 5) if GI then desires to place its
     initial firm order for Lot(s) of Probe Arrays directed to the Target
     Sequence, a firm order for the number of Lots desired by GI, it being
     understood that GI shall have the right to place its initial firm order for
     Lot(s) of Probe Arrays at any time prior to its advising AMTX pursuant to
     the last sentence of Section 3.3.3, and 6) the shipping location of the
     Probe Arrays, and 7) if GI desires for AMTX to store unpackaged Probe
     Arrays, GI's desired schedule for delivery of packaged Probe Arrays.  The
     foregoing good faith estimate of the number of Lots of Probe Arrays to be
     manufactured will not constitute a commitment on the part of GI to purchase
     more than one Lot of Probe Arrays for the particular Target Sequence, but
     will only be intended to aid AMTX in overall production planning processes.
     GI may request that the Probe Arrays meet specifications suggested by GI
     and not required herein, in which case AMTX will respond in good faith as
     to whether such additional specifications can reasonably be met and, if
     applicable, any cost increase to meet such additional specifications.

3.3  AMTX will promptly confirm receipt of the Target Sequence and provide a
     preliminary schedule for fabrication of Probe Arrays for the Target
     Sequence.  If  the information received 

                                       10

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


     by AMTX does not include the information required in paragraph 3.2 above, 
     AMTX will advise GI of any additional needed information.  Upon AMTX 
     confirming receipt of complete Target Sequence information ("AMTX 
     Confirmation"), AMTX will proceed to design, lay out,  produce masks,  
     and manufacture Probe Arrays for the Target Sequence as follows:

3.3.1     AMTX will cooperate with GI to review GI's selection of probe lengths
          and probe redundancy for the Target Sequence identified by GI.  AMTX
          will promptly deliver to GI a design description of the Probe Arrays
          to be fabricated for the particular Target Sequence.  Such design
          description will identify the oligonucleotide probes and layout of the
          probes, and will point out any suggested differences in probe lengths
          and probe redundancy that differ from that requested by GI.  AMTX will
          promptly produce prototype masks, produce and deliver a [   *   ] unit
          sample of Probe Arrays for design verification by GI ("Sample
          Delivery").  Sample Delivery will be accompanied by a certification by
          AMTX that the Probe Arrays delivered to GI meet the Fabrication
          Verification Criteria. 

3.3.2     If GI requests AMTX to revise the probe set (but not the Target
          Sequence) for a particular Probe Array design, AMTX will promptly
          provide GI with Optimization Probe Arrays.  Optimization Probe Arrays
          will be accompanied by a certification by AMTX that the Optimization
          Probe Arrays meet the Fabrication Verification Criteria.

3.3.3     GI may, within [   *   ] business days of Sample Delivery or delivery
          of Optimization Probe Arrays, evaluate any Probe Arrays delivered by
          AMTX to ensure that the Fabrication Verification Criteria are met.  If
          GI reasonably demonstrates that AMTX' certification is in error and
          that the Fabrication Verification Criteria are not met, AMTX will
          promptly fabricate an additional sample lot or set of Optimization
          Probe Arrays at no cost to GI.  Provided that the sample Probe Arrays
          or Optimization Probe Arrays meet the Fabrication Verification
          Criteria, GI will advise AMTX if it desires to have AMTX fabricate
          additional Optimization Probe Arrays, or full Lot(s) of  Probe Arrays,
          within [     *      ] business days of delivery of the applicable
          Sample Delivery or delivery of the last Optimization Probe Arrays.  At
          the same time that GI advises AMTX that it desires full Lot(s) of
          Probe Arrays, it shall place its  initial firm order for the number of
          Lots desired.

3.3.4     Provided that production of Probe Arrays for other Custom Chip
          Projects does not require 

                                       11

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


          production of Probe Arrays in excess of the Reserved Production 
          Capacity, within [     *      ] business days of GI's advising 
          that it desires to have full  Lots of Probe Arrays for a Custom 
          Chip Project,  AMTX will deliver to GI the Lot(s) of Probe Arrays 
          for that Custom Chip Project.  If production of Probe Arrays for a 
          Custom Chip Project would result in production rates for GI Probe 
          Arrays above the Reserved Production Capacity,  AMTX will schedule 
          the production of a Lot of Probe Arrays for the earliest date 
          reasonably consistent with AMTX' production schedule, but no later 
          than the next available time period when the Reserved Production 
          Capacity would not be exceeded for any other Custom Chip Project, 
          and will deliver such initial Lot(s) of Probe Arrays within 
          [      *      ] business days of the time when the Reserved 
          Production Capacity will not be exceeded.  AMTX will promptly 
          advise GI if the Reserved Production Capacity would be exceeded.

3.3.5     At any time following GI's initial placement of a firm order for
          Lot(s) of Probe Arrays for a particular Custom Chip Project, but
          before the end of the Resupply Term, GI may order additional Lots of
          Probe Arrays for a particular Custom Chip Project.  If the Reserved
          Production Capacity would not be exceeded, AMTX will deliver such
          additional Lots within [      *      ] business days of receipt of a
          written order for such additional Lots.  To the extent that orders of
          additional Lots of Probe Arrays would require AMTX to exceed the
          Reserved Production Capacity for GI, AMTX will schedule the production
          of such additional Lot(s) of Probe Arrays for the earliest date
          reasonably consistent with AMTX' production schedule, but no later
          than the next available time period when the Reserved Production
          Capacity for any other Custom Chip Project would not be exceeded, and
          will deliver such additional Lots of  Probe Arrays (or a portion
          thereof) within [      *      ] business days  of the first time when
          the Reserved Production Capacity will not be exceeded.  The Parties
          agree that this paragraph shall not obligate AMTX to store masks
          beyond the Resupply Term, provided that prior to destroying any masks,
          AMTX shall notify GI in writing and all such masks for GI Custom Chip
          Projects will, upon request of GI, be given to GI.

3.4  Probe Arrays will be packed in AMTX' standard shipping packages to the
     address specified by GI.  Deliveries will be F.O.B. AMTX' facility.  AMTX
     will ship via a carrier selected by GI or, if none is specified by GI, AMTX
     will select the carrier.  Title and risk of loss of 

                                       12

<PAGE>

     damage for deliveries will pass to GI upon AMTX' actual delivery of the 
     Probe Arrays to the carrier for shipment to GI.  GI will pay all 
     shipping costs.  GI will advise AMTX if insurance is desired on any 
     shipments of Probe Arrays, and will reimburse AMTX for all such 
     insurance charges. 

3.5  During the Resupply Term for Custom Chip Projects pursuant to this
     Agreement, GI may request an increase in the Reserved Production Capacity. 
     GI will compensate AMTX for such increased Reserved Production Capacity
     pursuant to Section 6.4 below.

3.6  GI may not 1) transfer the Probe Arrays provided by AMTX pursuant to this
     Agreement to any third party, other than to Affiliates and Collaborators
     during the course of and for the sole purpose of a GI Collaboration, or 2)
     provide services to any third party, other than to Affiliates and
     Collaborators, using the Probe Arrays provided by AMTX pursuant to the
     Agreement, or 3) allow any third party, other than Affiliates and
     Collborators during the course of a GI Collaboration, to use the Probe
     Arrays provided by AMTX under this Agreement, or 4) use the Probe Arrays
     delivered hereunder outside of GI's Area of Interest.  In the event that GI
     Collaborations result in a Novel Therapeutic Compound, such Novel
     Therapeutic Compound shall subject GI to the obligations to pay royalties
     and fees pursuant to Section 7.  Sample lots of Probe Arrays will be used
     only for evaluation of the performance of Probe Arrays and not for
     discovery of  Novel Therapeutic Compounds.

3.7  During the Resupply Term, GI  and its Affiliates and Collaborators may
     purchase hybridization stations and readers from AMTX or AMTX' suppliers in
     order to fully utilize the Probe Arrays purchased hereunder.

4    EXCLUSIVITY 

4.1  During and after any termination of this Agreement, AMTX will not 1) sell
     Probe Arrays designed for any of the Custom Chip Projects to any third
     party that incorporate any of the Confidential Information of GI or 2) use
     any computer files, or any other design information specific to the work
     conducted for GI,  generated in the design of  Probe Arrays fabricated
     pursuant to this Agreement to design probe arrays for any  third party,
     provided that AMTX will be able to sell probe arrays directed to a Target
     Sequence, or any portion thereof,  if such 

                                       13

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


     Target Sequence, or any portion thereof, is a) provided to AMTX by a 
     third party that did not develop the Target Sequence with the 
     Confidential Information of GI or b) independently developed by AMTX 
     without the Confidential Information of GI, and further provided that 
     the foregoing shall not confer on AMTX or any third party any rights 
     under the patent rights of GI. 

4.2  During the Resupply Term, GI will not buy Probe Arrays directed to a Target
     Sequence from a third party (when such third party infringes or would
     infringe the patent, copyright, or trade secret rights of AMTX or its
     Affiliates).  This paragraph shall not, during or after the Resupply
     Period, confer on GI or any third party any rights under the patent rights
     of AMTX.

4.3  AMTX  may make, have made, and use Probe Arrays designed for a Custom Chip
     Project for the purposes of improving its technology for manufacturing and
     using DNA probe arrays and for no other purposes.

4.4  In the event that AMTX is not able to supply Probe Arrays in amounts
     equaling GI's Reserved Production Capacity during the Resupply Term, GI may
     fabricate or have fabricated Probe Arrays to meet the Reserved Production
     Capacity.  Nothing in this paragraph, however, shall confer on GI or any
     third party any patent rights or other intellectual property rights from
     AMTX.

5    CONSULTING

5.1  The Parties do not anticipate that AMTX will be required to provide
     consulting services to GI under the terms of this Agreement during the term
     of the Collaboration Agreement.  After the term of the Collaboration
     Agreement, AMTX will provide GI with reasonable consulting services, if any
     are needed, in the design and development of assays and related technology
     needed to utilize the Probe Arrays delivered to GI hereunder according to
     the fee schedule in Section 6.5.

6    COMPENSATION

6.1  GI will pay to AMTX a flat fee of [   *   ] for each Custom Chip Project
     requiring Low Complexity Probe Arrays, and [   *   ] for each Custom Chip
     Project requiring High 

                                       14

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


     Complexity Probe Arrays.  Such payments will be payable in installments as 
     follows:

6.1.1     [        *        ] upon AMTX Confirmation for each Custom Chip
          Project.

6.1.2     [        *        ] within thirty (30) days of Sample Delivery which
          meets or, if Optimization Probe Arrays are produced, Optimization
          Probe Arrays which  meet the Fabrication Verification Criteria.

6.1.3     [        *       ] upon shipment of the first Lot for each Custom
          Chip Project.

6.2  For each sample of Optimization Probe Arrays shipped to GI, GI will pay to
     AMTX a flat fee of [  *  ] for the first [    *    ] of Optimization Probe
     Arrays, [  *  ] for the next [      *     ] of Optimization Probe Arrays,
     [  *  ] for the next [  *  ] of Optimization Probe Arrays, and [  *  ] for
     each set of Optimization Probe Arrays thereafter.

6.3  For each Lot of Probe Arrays for a Custom Chip Project (after the first Lot
     of Probe Arrays for a particular Custom Chip Project), GI will pay to AMTX:
     
6.3.1     [  *  ] upon shipment to GI of each Lot, when such order is made as
          part of GI's initial placement of a firm order for Lot(s) of Probe
          Arrays for a particular Custom Chip Project.

6.3.2     For each Lot ordered after GI's initial placement of a firm order for
          Lot(s) of Probe Arrays for a particular Custom Chip Project,  GI will
          pay [  *  ] per Lot for each of the first [  *  ] Lots shipped to GI,
          [  *  ] per Lot for each of the next [   *   ] Lots shipped to GI, and
          all subsequent Lots shipped to GI pursuant to this Agreement shall be
          [  *  ] per Lot.  For purposes of clarification, all additional Lots
          of Probe Arrays ordered by GI after GI's initial placement of a firm
          order for Lot(s) of Probe Arrays for a particular Custom Chip Project
          shall be counted towards such [     *     ] Lot totals, regardless of
          whether such Lots are for the same Custom Chip Project.

6.3.3     When ordering a Lot of Probe Arrays, GI may specify that all or a
          portion of such Lot shall not be packaged and that AMTX will store
          such unpackaged Probe Arrays.  AMTX will store such Probe Arrays for
          up to [    *    ],  provided that such Probe Arrays will be deemed
          delivered to GI when they are ready for packaging, for purposes of the
          payments due hereunder, but not for purposes of the warranty
          provisions hereunder.  GI may request, at any time, delivery of groups
          of [ * ] or more stored Probe Arrays that are then currently in 
          storage by AMTX at no additional cost.

                                       15

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


6.3.4     In the event that GI wishes to order an odd Lot (i.e., an amount other
          than a multiple of [ * ]) of Probe Arrays (after the first Lot), AMTX
          will quote pricing for such odd Lots upon request of GI.

6.4  If GI desires additional Reserved Production Capacity, AMTX will provide a
     quote for the cost of such additional Reserved Production Capacity.  If GI
     desires to obtain such additional Reserved Production Capacity at the
     quoted cost, AMTX will proceed to use reasonable efforts to provide such
     additional Reserved Production Capacity.

6.5  Consulting services shall be invoiced at the rate of [  *  ] per day plus
     expenses when AMTX is provided [ * ] or fewer days of notice, or [  *  ] 
     per day plus expenses when more than [ * ] days of notice is provided.

6.6  All amounts referred to in this Section will be invoiced by AMTX when due. 
     All payments will be made to AMTX thirty (30) days from the date of
     invoicing by AMTX.  AMTX shall promptly provide GI with written notice of
     any late payments.  Late payments shall bear interest at the rate of [ * ]
     per month.

6.7  In the event that GI desires to have Probe Arrays manufactured that utilize
     probes of more than [       *       ], AMTX will determine if its current
     design and manufacturing capabilities permit the reliable manufacture of
     Probe Arrays with more than [       *       ].  If AMTX concludes that it
     can reliably manufacture such Probe Arrays, AMTX will provide revised
     pricing for such Probe Arrays.   

6.8  Hybridization stations and readers may be purchased by GI and its
     Affiliates and Collaborators at the lower of 1) the cost calculated
     pursuant to the Collaboration Agreement, and 2) the price for which such
     hybridization stations and readers are generally sold by AMTX to third
     parties.

7    FEES AND ROYALTIES

7.1  GI shall pay AMTX fees as follows for each Novel Therapeutic Compound
     resulting from a Custom Chip Project, up to a maximum of [   *   ] for each
     Custom Chip Project involving Low Complexity Probe Arrays and [    *    ]
     for each Custom Chip Project involving High Complexity Probe Arrays.

                                       16

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


7.1.1     In the event that GI or any of its Affiliates or Collaborators 
          discovers a therapeutic use for a protein through the use of Probe 
          Arrays and files either (1) a patent application covering such 
          therapeutic use, or (2) a declaration in support of a patent 
          application previously filed by GI or any of its Affiliates or 
          Collaborators covering the gene from which the protein is expressed 
          and/or the protein itself where such declaration includes the 
          biological activity data relating to such  therapeutic use, GI 
          shall pay AMTX a fee of [  *  ] upon the first such filing made for 
          each such protein and a fee of [  *  ] upon the issuance of the 
          first patent claiming the therapeutic use for each such protein.  

7.1.2     In the event that GI or any of its Affiliates or Collaborators
          discovers a gene encoding for a protein having a therapeutic use
          through the use of  Probe Arrays and files a patent application
          covering the gene from which the protein is expressed and/or the
          protein itself, GI shall pay AMTX a fee of [  *  ] upon the first
          such patent filing made for each such protein  and a fee of [  *  ]
          upon the issuance of the first patent claiming the gene and/or the
          protein itself for each such protein.

7.1.3     For the first  IND filing directed to a Novel Therapeutic Compound, GI
          shall pay to AMTX a fee of [  *  ].

7.1.4     Payments made pursuant to Sections 7.1.1, 7.1.2 and 7.1.3 shall be
          subject to the maximums set forth in Section 7.1.

7.2  GI shall pay AMTX a running royalty of [ * ] of Net Sales by GI, its
     Affiliates, Collaborators, licensees, and sublicensees for each Novel
     Therapeutic Compound having a label referring to a Novel Use Therapeutic
     and [ * ] of Net Sales by GI, its Affiliates, Collaborators, licensees, and
     sublicensees for each Novel Gene Therapeutic. Such royalties shall only be
     payable on Novel Therapeutic Compounds where the Novel Use Therapeutic or
     Novel Gene Therapeutic that is discovered  through use of the Probe Arrays
     is covered by a Patent Claim.  In no event shall GI be required to pay a
     royalty of more than [       *       ] of Net Sales.

7.3  GI shall deliver to AMTX, within sixty (60) days after the end of each
     calendar quarter, a written report showing its computation of payments due
     under this Agreement, including any Net Sales by GI, its Affiliates,
     Collaborators, licensees, and sublicensees during such calendar 

                                       17

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


     quarter. All Net Sales shall be segmented in each such report according 
     to sales by GI, each Affiliate, Collaborator, licensee, and sublicensee, 
     as well as on a country by country basis, including the rates of 
     exchange used to convert such royalties to U.S. Dollars from the 
     currency in which the sales were made.  For the purposes of this 
     Agreement, the rates of exchange to be used for converting royalties to 
     U.S. Dollars shall be those published for the purchase of U.S. Dollars 
     in the East Coast Edition of the Wall Street Journal for the last 
     business day of the calendar quarter for which payment is due.  
     Simultaneously with the delivery of each such report, GI shall tender 
     payment in U.S. Dollars of all royalties shown to be due therein. Where 
     royalties are due for sales of products in a country where, by reason of 
     currency regulations it is impossible or illegal for GI, its Affiliates, 
     Collaborators, licensees or sublicenses to transfer royalty payments to 
     AMTX, such royalties shall be deposited in whatever currency is 
     allowable in an accredited bank in that country that is reasonably 
     acceptable to AMTX.  Any and all income or similar taxes imposed or 
     levied on account of the receipt of royalties payable under this 
     Agreement which are required to be withheld by GI shall be paid by GI on 
     behalf of AMTX and shall be paid to the proper taxing authority.  Proof 
     of payment shall be secured and sent to AMTX as evidence of such payment 
     in such form as required by the tax authorities having jurisdiction over 
     GI or its Affiliates, Collaborators, licensees, or sublicensees.  Such 
     taxes shall be deducted from the royalty that would otherwise be 
     remitted by GI or its Affiliates, Collaborators, licensees, or 
     sublicensees.  Late payments shall bear interest at the rate of [  *  ] 
     per month.

8    INTELLECTUAL PROPERTY

8.1  Any inventions conceived or first reduced to practice during performance of
     this Agreement and arising from performance of this Agreement (Project
     Inventions) shall be assigned according to inventorship of such inventions.
     While not anticipated, in the event that AMTX is deemed to be the joint or
     sole inventor of a Project Invention directed to Novel Therapeutic
     Compounds or genes related thereto, AMTX shall assign such Project
     Invention to GI.  GI grants to AMTX and its Affiliates a royalty free,
     nonexclusive, nonsublicensable, worldwide perpetual license under all GI
     Project Inventions relating to the development, use, 

                                       18

<PAGE>

     manufacture, distribution, and/or sale of Probe Arrays, except as to 
     those GI Project Inventions relating to Novel Therapeutic Compounds  and 
     genes related thereto.  Each Party shall bear all cost incurred by it in 
     acquiring patent rights for Project Inventions. 

8.2  Except as specifically provided herein, no implied license rights under any
     patents, copyrights, or trade secrets are conveyed by one Party to another
     Party pursuant to this Agreement by implication or otherwise.

9    CONFIDENTIALITY

9.1  Each Party shall maintain the Confidential Information of the other Party
     in confidence, 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:

9.1.1     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

9.1.2     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;

9.1.3     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 on the party of the receiving Party or its
          Affiliates; or

9.1.4     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.  

                                       19

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


10   WARRANTY

10.1 GI  represents and warrants to AMTX that it has the full right and
     authority to enter into and perform this Agreement.  
10.2 AMTX represents and warrants to GI that (1) it has the full right and
     authority to enter into and perform this Agreement, (2) it has the right or
     has obtained the necessary consents, waivers, approvals or other
     authorizations to make the assignments provided for in Section 8.1 of this
     Agreement, and (3) it has obtained from Glaxo Wellcome plc and its
     affiliated entities (the "Glaxo Entities") any and all consents, waivers,
     approvals or other authorizations necessary to enter into and perform this
     Agreement without violating the terms of its agreements with the Glaxo
     Entities.  AMTX hereby agrees to indemnify, defend, protect and hold
     harmless GI and its Affiliates and its Collaborators against any and all
     losses, costs, damages, expenses, fees and/or liabilities directly or
     indirectly resulting from any claims, lawsuits and/or judgments ("Claims")
     to the extent that such Claims are based on allegations predicated on the
     foregoing representations and warranties being false.  

10.3 AMTX warrants that the Probe Arrays will meet the Fabrication Verification
     Criteria  at the time they are delivered to GI.  AMTX warrants that the
     Probe Arrays delivered hereunder do not incorporate the trade secret or
     copyright rights of a third party.  AMTX 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.  [
     
     
     
     
                                       *
     
     
     
                                                                       ].

                                       20

<PAGE>

                    CONFIDENTIAL TREATMENT REQUESTED


10.4 If GI believes that AMTX is in breach of the warranty provisions herein as
     to delivery of full Lots of Probe Arrays, GI will notify AMTX in writing
     within [     *      ] business days of receipt of any nonconformity of the
     Probe Arrays.  In the absence of such notice all Probe Arrays shall be
     conclusively deemed accepted and GI may not revoke its acceptance.  

11   INDEMNITY 

11.1 [
     
     
     
     
     
     
     
     
     
     
     
                                        *
     
     
     
     
     
     
                                                              ].

                                       21

<PAGE>

12   TERM AND TERMINATION

12.1 This Agreement shall extend until the end of the Resupply Term, unless
     extended by written agreement of both Parties.

12.2 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 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.

12.3 In the event that GI reasonably determines that it is necessary for it to
     obtain a license or similar right from a third party in the absence of 
     which it could not legally use the Probe Arrays in GI's Area of Interest 
     without infringing such third party's intellectual property rights, GI 
     shall have the right to terminate this Agreement upon written notice to 
     AMTX, provided that (1) GI shall have used diligent efforts to secure 
     such license or similar right and (2) the third party shall have failed 
     to make a license or similar right available to GI on commercially 
     reasonable terms, and (3) the failure to obtain such license or similar 
     right shall leave GI with no meaningful way to utilize the Probe Arrays 
     contemplated to be designed and purchased hereunder.

12.4 Upon termination of this Agreement, the following provisions will survive: 
     4.1, 7, 8, 9, 11 and 13.

13   MISCELLANEOUS

13.1 GI shall keep, and shall cause its Affiliates, Collaborators, licensees,
     and sublicensees to keep, for a period of at least two (2) years full, 
     accurate, and true books of accounts and other records containing all 
     information and data which may be necessary to ascertain and verify the 
     royalties and fees payable hereunder.  During the term of this Agreement 
     and for a period of two (2) years following the time at which the 
     relevant fee or payment is due, AMTX shall have the right from time to 
     time (not to exceed once during a calender year) to inspect in 
     confidence, or have an agent, accountant, or representative inspect in 
     confidence such books, records, and supporting data.

                                       22

<PAGE>

13.2 GI UNDERSTANDS THAT THE PROBE ARRAYS DELIVERED HEREUNDER ARE NOT FDA
     APPROVED.  GI AGREES NOT TO USE THE PROBE ARRAYS DELIVERED HEREUNDER IN 
     ANY CLINICAL OR OTHER SETTING REQUIRING FDA APPROVAL.

13.3 Neither Party nor any of its Affiliates shall originate any publicity, news
     release, or other public announcement, written or oral, relating to this 
     Agreement or the existence of an arrangement between the Parties without 
     the prior written approval of the other Party, which approval shall not 
     be unreasonably withheld, except as otherwise required by law.

13.4 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. 

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

13.6 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.

13.7 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.

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

13.9 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 

                                       23

<PAGE>

     particular provision(s) held to be unenforceable. 

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

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

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

          If to GI: 

                   Genetics Institute, Inc.
                   87 CambridgePark Drive
                   Cambridge, Massachusetts 02140
                   Attn: General Counsel

          If to AMTX:

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

13.13     The Parties shall not be liable or 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. 

                                       24

<PAGE>

13.14     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.

 /s/  STEPHEN P.A. FODOR
- --------------------------

By:  Stephen P.A. Fodor
     President
    ----------------------

Date:  December 8, 1995
      --------------------

Genetics Institute, Inc.

    /s/  JACK MORGAN
- --------------------------

By:       Jack Morgan
    ----------------------

Date:   December 13, 1995
      --------------------

                                       25

<PAGE>

                                 CONFIDENTIAL
                                  TREATMENT
                                  REQEUESTED
 
                                   EXHIBIT A

               EXPRESSION CHIPS:  [

     






     




                                       *






















                                ].


                                       26


<PAGE>

                                 CONFIDENTIAL
                                  TREATMENT
                                  REQEUESTED


                                   EXHIBIT B

                      FABRICATION VERIFICATION CRITERIA


[


                                       *




                                          ].




                                       27



<PAGE>
                                                                    EXHIBIT 23.1
 
               CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS
 
   
    We  consent  to  the reference  to  our  firm under  the  captions "Selected
Financial Data" and "Experts"  and to the  use of our  report dated February  9,
1996  (except for the first paragraph of Note 9, as to which the date is May 20,
1996), in Amendment No. 3 to the Registration Statement (Form S-1 No.  333-3648)
and  related Prospectus  of Affymetrix, Inc.  for the  registration of 6,900,000
shares of its common stock.
    
 
                                          ERNST & YOUNG LLP
   
Palo Alto, California
June 3, 1996
    

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                                                                   EXHIBIT 23.3

                  CONSENT OF TOWNSEND AND TOWNSEND AND CREW LLP


     We consent to the reference to our firm under the caption "Experts" in 
Amendment No. 3, dated June 3, 1996, of the Registration Statement on Form S-1 
and related Prospectus of Affymetrix, Inc. for the registraion of 6,900,000 
shares of its common stock.


                                       TOWNSEND AND TOWNSEND AND CREW LLP


                                       By: /s/ Paul C. Haughey
                                          ------------------------------------
                                          Paul C. Haughey
                                          Partner


Palo Alto, California
June 3, 1996




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