Document:

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                                                                  EXECUTION COPY

                               Up to $225,000,000

                                Affymetrix, Inc.

                  4.75% Convertible Subordinated Notes due 2007

                          REGISTRATION RIGHTS AGREEMENT

                                                               February 14, 2000

Credit Suisse First Boston Corporation,
as Representative of the several Initial
Purchasers referred to herein,
c/o Credit Suisse First Boston Corporation
Eleven Madison Avenue
New York, New York  10010-3629

Dear Sirs:

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                                                                            2

                  Affymetrix, Inc., a Delaware corporation (the "Company"),
proposes to issue and sell to Credit Suisse First Boston Corporation ("CSFBC")
and the other initial purchasers named in Schedule A to the Purchase Agreement
(as defined below) (collectively, the "Initial Purchasers"), upon the terms set
forth in a purchase agreement dated as of February 8, 2000 (the "Purchase
Agreement") between the Company and the Initial Purchasers, $175,000,000
aggregate principal amount (plus up to an additional $50,000,000 principal
amount) of 4.75% Convertible Subordinated Notes Due 2007 (the "Notes") of the
Company. The Notes will be convertible into shares of Common Stock, par value
$0.01 per share, of the Company (the "Common Stock") at the conversion price set
forth in the Offering Circular dated February 8, 2000. The Notes will be issued
pursuant to an Indenture, dated as of February 14, 2000 (the "Indenture"),
between the Company and The Bank of New York (the "Trustee"). As an inducement
to the Initial Purchasers to enter into the Purchase Agreement and in
satisfaction of a condition to the Initial Purchasers' obligations thereunder,
the Company agrees with the Initial Purchasers, (i) for the benefit of the
Initial Purchasers and (ii) for the benefit of the holders of the Notes and the
Common Stock issuable upon conversion of the Notes (collectively, the
"Securities") from time to time until such time as such Securities have been
sold pursuant to a Shelf Registration Statement (as defined below) (each of the
foregoing a "Holder" and together the "Holders"), as follows:

                  1. SHELF REGISTRATION. The Company shall take the following
actions:

                  (a) The Company shall, at its cost, prepare and, as promptly
as practicable (but in no event more than 90 days after so required or requested
pursuant to this Section 1) file with the Securities and Exchange Commission
(the "Commission") and thereafter shall use its commercially reasonable best
efforts to cause to be declared effective as soon as practicable a registration
statement on Form S-3 (the "Shelf Registration Statement") covering the offer
and sale of the Transfer Restricted Securities (as defined in Section 5 hereof)
by the Holders thereof from time to time in accordance with the methods of
distribution set forth in the Shelf Registration Statement and Rule 415 under
the Securities Act of 1933, as amended (the "Securities Act") (hereinafter, the
"Shelf Registration"); PROVIDED, HOWEVER, that no Holder (other than the Initial
Purchasers) shall be entitled to have the Securities held by it covered by such
Shelf Registration Statement unless such Holder agrees in writing to be bound by
all the provisions of this Agreement applicable to such Holder.

                  (b) The Company shall use its commercially reasonable best
efforts to keep the Shelf Registration Statement

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continuously effective in order to permit the prospectus included therein (the
"Prospectus") to be lawfully delivered by the Holders of the relevant
Securities, for a period of two years (or for such longer period if extended
pursuant to Section 2(h) below) from the date of its effectiveness or such
shorter period that will terminate when all the Securities covered by the Shelf
Registration Statement (i) have been sold pursuant thereto or (ii) may be sold
pursuant to Rule 144(k) under the Securities Act (or any successor rule
therefore), assuming for this purpose that the Holders thereof are not
affiliates of the Company (in any such case, such period being called the "Shelf
Registration Period"). The Company shall be deemed not to have used its
commercially reasonable best efforts to keep the Shelf Registration Statement
effective during the requisite period if it voluntarily takes any action that
would result in Holders of Securities covered thereby not being able to offer
and sell such Securities during that period, unless such action is (i) required
by applicable law or (ii) taken by the Company in good faith and for valid
business reasons upon the occurrence of any event contemplated by Section
2(b)(v) below, and the Company thereafter complies with the requirements of
Section 2(h).

                  (c)  Notwithstanding any other provisions of this
Agreement to the contrary, the Company shall cause the Shelf Registration
Statement and the Prospectus and any amendment or supplement thereto, as of the
effective date of the Shelf Registration Statement, amendment or supplement, (i)
to comply in all material respects with the applicable requirements of the
Securities Act and the rules and regulations of the Commission and (ii) not to
contain any untrue statement of a material fact or omit to state a material fact
required to be stated therein or necessary to make the statements therein, in
light of the circumstances under which they were made, not misleading.

                  2.  REGISTRATION PROCEDURES.  In connection with the Shelf
Registration contemplated by Section 1 hereof, the following provisions shall
apply:

                  (a) The Company shall (i) furnish to each of the Initial
Purchasers, prior to the filing thereof with the Commission, a copy of the Shelf
Registration Statement and each amendment thereof and each amendment or
supplement, if any, to the prospectus included therein and, in the event that an
Initial Purchaser (with respect to any portion of an unsold allotment from the
original offering) is participating in the Shelf Registration Statement, use its
commercially reasonable best efforts to reflect in each such document, when so
filed with the Commission, such comments as such Initial Purchaser reasonably
may propose and (ii) include the names of the Holders who propose to sell
Securities pursuant to the Shelf Registration Statement, as selling security
holders.

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                  (b) The Company shall give written notice to the Initial
Purchasers and the Holders (which notice pursuant to clauses (ii)-(v) hereof
shall be accompanied by an instruction to suspend the use of the prospectus
until the requisite changes have been made):

                  (i) when the Shelf Registration Statement or any amendment
         thereto has been filed with the Commission and when the Shelf
         Registration Statement or any post-effective amendment thereto has
         become effective;

                  (ii) of any request by the Commission for amendments or
         supplements to the Shelf Registration Statement or the
         prospectus included therein or for additional information;

                  (iii) of the issuance by the Commission of any stop order
         suspending the effectiveness of the Shelf Registration Statement or the
         initiation of any proceedings for that purpose;

                  (iv) of the receipt by the Company or its legal counsel
         of any notification with respect to the suspension of the
         qualification of the Securities for sale in any jurisdiction or the
         initiation or threatening of any proceeding for such purpose; and

                  (v) of the happening of any event or circumstance that would
         require the Company to make changes in the Shelf Registration Statement
         or the Prospectus in order that the Shelf Registration Statement or the
         Prospectus does not contain an untrue statement of a material fact nor
         omit to state a material fact required to be stated therein or
         necessary to make the statements therein (in the case of the
         Prospectus, in light of the circumstances under which they were made)
         not misleading, which written notice need not provide any detail as to
         the nature of such event.

                  (c) The Company shall make every reasonable effort to obtain
the withdrawal, at the earliest possible time, of any order suspending the
effectiveness of the Shelf Registration Statement.

                  (d) The Company shall furnish to each Holder of Securities
included within the coverage of the Shelf Registration, without charge, at least
one copy of the Shelf Registration Statement and any post-effective amendment
thereto, including financial statements and schedules, and, if the Holder so
requests in writing, all exhibits thereto (including those, if any, incorporated
by reference).

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                  (e) The Company shall, during the Shelf Registration Period,
deliver to each Holder of Securities included within the coverage of the Shelf
Registration Statement, without charge, as many copies of the Prospectus
(including each preliminary prospectus) included in the Shelf Registration
Statement and any amendment or supplement thereto as such person may reasonably
request. The Company consents, subject to the provisions of this Agreement, to
the use of the Prospectus or any amendment or supplement thereto by each of the
selling Holders in connection with the offering and sale of the Securities
covered by the Prospectus, or any amendment or supplement thereto, included in
the Shelf Registration Statement.

                  (f) Prior to any public offering of the Securities pursuant to
the Shelf Registration Statement, the Company shall register or qualify or
cooperate with the Holders of the Securities included therein and their
respective counsel in connection with the registration or qualification of such
Securities for offer and sale under the securities or "blue sky" laws of such
states of the United States as any such Holder reasonably requests in writing
and do any and all other acts or things necessary or advisable to enable the
offer and sale in such jurisdictions of the Securities covered by the Shelf
Registration Statement; PROVIDED, HOWEVER, that the Company shall not be
required to (i) qualify generally to do business in any jurisdiction
where it is not then so qualified or (ii) take any action which would subject it
to general service of process or to taxation in any jurisdiction where it is not
then so subject.

                  (g) The Company shall cooperate with the Holders of the
Securities to facilitate the timely preparation and delivery of certificates
representing the Securities to be sold pursuant to the Shelf Registration
Statement free of any restrictive legends and in such denominations and
registered in such names as the Holders may request a reasonable period of time
prior to sales of the Securities pursuant to the Shelf Registration Statement.

                  (h) Upon the occurrence of any event contemplated by
paragraphs (ii) through (v) of Section 2(b) above during the period for which
the Company is required to maintain an effective Shelf Registration Statement,
the Company shall, as required hereby, prepare and file a post-effective
amendment to the Shelf Registration Statement or an amendment or supplement to
the Prospectus and any other required document so that, as thereafter delivered
to Holders or purchasers of Securities, the Prospectus will not contain an
untrue statement of a material fact or omit to state any material fact required
to be stated therein or necessary to make the statements therein, in light of
the circumstances under which they were made, not misleading. If the Company
notifies the Initial Purchasers and the Holders in

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accordance with paragraphs (ii) through (v) of Section 2(b) above to suspend the
use of the Prospectus until the requisite changes to the Prospectus have been
made, then the Initial Purchasers and the Holders shall suspend use of such
prospectus and the period of effectiveness of the Shelf Registration Statement
provided for in Section 1(b) above shall be extended by the number of days from
and including the date of giving such notice to and including the date when the
Initial Purchasers and the Holders shall have received such amended or
supplemented prospectus pursuant to this Section 2(h). Any such amendment,
supplement or document will be prepared and filed as promptly as practicable
under the circumstances, as determined in good faith by the Company, it being
understood that the Company may have bona fide reasons to delay such preparation
and filing for a period which may not in any event exceed 60 days.

                  (i) Not later than the effective date of the Shelf
Registration Statement, the Company will provide CUSIP numbers for the Notes and
the Common Stock registered under the Shelf Registration Statement, and provide
the Trustee with printed certificates for such Notes, in a form eligible for
deposit with The Depository Trust Company.

                  (j) The Company will comply with all rules and regulations of
the Commission to the extent and so long as they are applicable to the Shelf
Registration and will make generally available to its security holders (or
otherwise provide in accordance with Section 11(a) of the Securities Act) an
earnings statement satisfying the provisions of Section 11(a) of the Securities
Act, no later than 45 days after the end of a 12-month period (or 90 days, if
such period is a fiscal year) beginning with the first month of the Company's
first fiscal quarter commencing after the effective date of the Shelf
Registration Statement, which statement shall cover such 12-month period.

                  (k) The Company shall cause the Indenture to be qualified
under the Trust Indenture Act of 1939, as amended (the "Trust Indenture Act"),
in a timely manner and containing such changes, if any, as shall be necessary
for such qualification. In the event that such qualification would require the
appointment of a new trustee under the Indenture, the Company shall appoint a
new trustee thereunder pursuant to the applicable provisions of the Indenture.

                  (l) The Company may require each Holder of Securities to be
sold pursuant to the Shelf Registration Statement to furnish to the Company such
information regarding the Holder and the distribution of the Securities as the
Company may from time to time reasonably require for inclusion in the Shelf
Registration Statement, and the Company may exclude from such registration the
Securities of any Holder that fails to furnish

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such information within a reasonable time after receiving such request.

                  (m) The Company shall enter into such customary agreements
(including, if requested, an underwriting agreement in customary form) and take
all other actions, if any, as any Holder shall reasonably request in order to
facilitate the disposition of the Securities pursuant to the Shelf Registration,
PROVIDED, HOWEVER, that the Company shall not be required to facilitate an
underwritten offering pursuant to the Shelf Registration Statement by any
Holders unless the offering relates to at least $50,000,000 principal amount of
the Notes or the equivalent number of shares of Common Stock into which such
Notes are convertible.

                  (n) The Company shall (i) make reasonably available for
inspection by the Holders, any underwriter participating in any distribution
pursuant to the Shelf Registration Statement and any attorney, accountant or
other agent retained by the Holders or any such underwriter, all relevant
financial and other records, pertinent corporate documents and properties of the
Company and (ii) cause the Company's officers, directors, employees, accountants
and auditors to supply all relevant information reasonably requested by the
Holders or any such underwriter, attorney, accountant or agent in connection
with the Shelf Registration Statement, in each case, as shall be reasonably
necessary to enable such persons to conduct a reasonable investigation within
the meaning of Section 11 of the Securities Act; PROVIDED, HOWEVER, that the
foregoing inspection and information gathering (i) shall be coordinated on
behalf of the Initial Purchasers by you and on behalf of the other parties, by
one counsel designated by and on behalf of the other parties as described in
Section 3 hereof.

                  (o) The Company, if requested by any Holder of Securities
covered by Shelf Registration Statement, shall cause (i) its counsel (which may
include the Company's general counsel for one or more of the opinions) to
deliver an opinion and updates thereof relating to the Securities in customary
form addressed to such Holders and the managing underwriters, if any, thereof,
and dated, in the case of the initial opinion, the effective date of the Shelf
Registration Statement (it being agreed that the matters to be covered by such
opinion shall include, without limitation, (A) the due incorporation and good
standing of the Company; (B) the qualification of the Company to transact
business as a foreign corporation; the due authorization, execution and delivery
of the relevant agreement of the type referred to in Section 2(m) hereof; (C)
the due authorization, execution, authentication and issuance, and the validity
and enforceability, of the Securities; (D) the absence of material legal or
governmental proceedings involving the

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Company; (E) the absence of governmental approvals required to be obtained in
connection with the Shelf Registration Statement, the offering and sale of the
Securities, or any agreement of the type referred to in Section 2(m) hereof; (F)
the compliance as to form of the Shelf Registration Statement and any documents
incorporated by reference therein and of the Indenture with the requirements of
the Securities Act and the Trust Indenture Act, respectively; and, (G) as of the
date of the opinion and as of the effective date of the Shelf Registration
Statement or most recent post-effective amendment thereto, as the case may be,
the absence from the Shelf Registration Statement and the prospectus included
therein, as then amended or supplemented, and from any documents incorporated by
reference therein of an untrue statement of a material fact or the omission to
state therein a material fact required to be stated therein or necessary to make
the statements therein not misleading (in the case of any such documents, in the
light of the circumstances existing at the time that such documents were filed
with the Commission under the Securities Exchange Act of 1934, as amended (the
"Exchange Act"), it being understood that the items contained in this clause (G)
may be in the form of a statement), (ii) its officers to execute and deliver all
customary documents and certificates and updates thereof requested by any
underwriters of the Securities or counsel for the Holders and (iii) its
independent public accountants and the independent public accountants with
respect to any other entity for which financial information is provided in the
Shelf Registration Statement to provide to the selling Holders of the Securities
and any underwriter therefor a comfort letter in customary form and covering
matters of the type customarily covered in comfort letters in connection with
primary underwritten offerings, subject to receipt of appropriate documentation
as contemplated, and only if permitted, by Statement of Auditing Standards
No. 72.

                  (p) The Company shall use its best efforts to take all other
steps necessary to effect the registration of the Securities covered by the
Shelf Registration Statement.

                  3. REGISTRATION EXPENSES. The Company shall bear all fees and
expenses incurred in connection with the performance of its obligations under
Sections 1 and 2 hereof (including the reasonable fees and expenses, if any, of
counsel for the Initial Purchasers, incurred in connection with the Shelf
Registration), whether or not the Shelf Registration Statement is filed or
becomes effective, and shall bear or reimburse the Holders of the Securities
covered by the Shelf Registration for the reasonable fees and disbursements of
one firm of counsel designated by the Holders of a majority in principal amount
of the Securities covered by the Shelf Registration Statement (provided that
Holders of Common Stock issued upon the conversion of the Notes shall be deemed
to be Holders of the aggregate principal amount

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of Notes from which such Common Stock was converted) to act as counsel for the
Holders in connection therewith.

                  4. INDEMNIFICATION. (a) The Company agrees to indemnify and
hold harmless each Holder and each person, if any, who controls such Holder
within the meaning of the Securities Act or the Exchange Act (each Holder and
such controlling persons are referred to collectively as the "Indemnified
Parties") from and against any losses, claims, damages or liabilities, joint or
several, or any actions in respect thereof (including, but not limited to, any
losses, claims, damages, liabilities or actions relating to purchases and sales
of the Securities) to which each Indemnified Party becomes subject under the
Securities Act, the Exchange Act or otherwise, insofar as such losses, claims,
damages, liabilities or actions arise out of or are based upon any untrue
statement or alleged untrue statement of a material fact contained in the Shelf
Registration Statement or Prospectus, including any document incorporated by
reference therein, or in any amendment or supplement thereto or in any
preliminary prospectus relating to the Shelf Registration, or arise out of, or
are based upon, the omission or alleged omission to state therein a material
fact required to be stated therein or necessary to make the statements therein
not misleading, and shall reimburse, as incurred, the Indemnified Parties for
any legal or other expenses reasonably incurred by them in connection with
investigating or defending any such loss, claim, damage, liability or action in
respect thereof; PROVIDED, HOWEVER, that (i) the Company shall not be liable in
any such case to the extent that such loss, claim, damage or liability arises
out of or is based upon any untrue statement or alleged untrue statement or
omission or alleged omission made in the Shelf Registration Statement or
Prospectus or in any amendment or supplement thereto or in any preliminary
prospectus relating to the Shelf Registration in reliance upon and in conformity
with written information pertaining to such Holder and furnished to the Company
by or on behalf of such Holder specifically for inclusion therein and (ii) with
respect to any untrue statement or omission or alleged untrue statement or
omission made in any preliminary prospectus relating to the Shelf Registration
Statement, the indemnity agreement contained in this subsection (a) shall not
inure to the benefit of any Holder from whom the person asserting any such
losses, claims, damages or liabilities purchased the Securities concerned, to
the extent that a prospectus relating to such Securities was required to be
delivered by such Holder under the Securities Act in connection with such
purchase and any such loss, claim, damage or liability of such Holder results
from the fact that there was not sent or given to such person, at or prior to
the written confirmation of the sale of such Securities to such person, a copy
of the final prospectus if the Company had previously furnished copies thereof
to such Holder; PROVIDED FURTHER, HOWEVER, that this indemnity agreement will be
in

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addition to any liability which the Company may otherwise have to such
Indemnified Party.

                  The Company shall also indemnify the underwriters, their
officers and directors and each person who controls such underwriters within the
meaning of the Securities Act or the Exchange Act to the same extent as provided
above with respect to the indemnification of the Holders if requested by such
Holders.

                  (b) Each Holder, severally and not jointly, will indemnify and
hold harmless the Company, its officers and directors and each person, if any,
who controls the Company within the meaning of the Securities Act or the
Exchange Act from and against any losses, claims, damages or liabilities or any
actions in respect thereof, to which the Company or any such controlling person
may become subject under the Securities Act, the Exchange Act or otherwise,
insofar as such losses, claims, damages, liabilities or actions arise out of or
are based upon any untrue statement or alleged untrue statement of a material
fact contained in a Shelf Registration Statement or prospectus or in any
amendment or supplement thereto or in any preliminary prospectus relating to a
Shelf Registration, or arise out of or are based upon the omission or alleged
omission to state therein a material fact necessary to make the statements
therein not misleading, but in each case only to the extent that the untrue
statement or omission or alleged untrue statement or omission was made in
reliance upon and in conformity with written information pertaining to such
Holder and furnished to the Company by or on behalf of such Holder specifically
for inclusion therein; and, subject to the limitation set forth immediately
preceding this clause, shall reimburse, as incurred, the Company for any legal
or other expenses reasonably incurred by the Company or any such controlling
person in connection with investigating or defending any loss, claim, damage,
liability or action in respect thereof. This indemnity agreement will be in
addition to any liability which such Holder may otherwise have to the Company or
any of its controlling persons.

                  (c) Promptly after receipt by an indemnified party under this
Section 4 of notice of the commencement of any action or proceeding (including a
governmental investigation), such indemnified party will, if a claim in respect
thereof is to be made against the indemnifying party under this Section 4,
notify the indemnifying party of the commencement thereof; but the omission so
to notify the indemnifying party will not, in any event, relieve the
indemnifying party from any obligations to any indemnified party other than the
indemnification obligation provided in subsections (a) or (b) above. In case any
such action is brought against any indemnified party, and it notifies the
indemnifying party of the commencement thereof, the indemnifying party will be
entitled to participate therein and,

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to the extent that it may wish, jointly with any other indemnifying party
similarly notified, to assume the defense thereof, with counsel reasonably
satisfactory to such indemnified party (who shall not, except with the consent
of the indemnified party, be counsel to the indemnifying party), and after
notice from the indemnifying party to such indemnified party of its election so
to assume the defense thereof the indemnifying party will not be liable to such
indemnified party under this Section 4 for any legal or other expenses, other
than reasonable costs of investigation, subsequently incurred by such
indemnified party in connection with the defense thereof. No indemnifying party
shall, without the prior written consent of the indemnified party, effect any
settlement of any pending or threatened action in respect of which any
indemnified party is or could have been a party and indemnity could have been
sought hereunder by such indemnified party unless such settlement includes an
unconditional release of such indemnified party from all liability on any claims
that are the subject matter of such action.

                  (d) If the indemnification provided for in this Section 4 is
unavailable or insufficient to hold harmless an indemnified party under
subsections (a) or (b) above, then each indemnifying party shall contribute to
the amount paid or payable by such indemnified party as a result of the losses,
claims, damages or liabilities (or actions in respect thereof) referred to in
subsections (a) or (b) above (i) in such proportion as is appropriate to reflect
the relative benefits received by the indemnifying party or parties on the one
hand and the indemnified party on the other from the registration of the
Securities, pursuant to the Shelf Registration, or (ii) if the allocation
provided by the foregoing clause (i) is not permitted by applicable law, in such
proportion as is appropriate to reflect not only the relative benefits referred
to in clause (i) above but also the relative fault of the indemnifying party or
parties on the one hand and the indemnified party on the other in connection
with the statements or omissions that resulted in such losses, claims, damages
or liabilities (or actions in respect thereof) as well as any other relevant
equitable considerations. The relative fault of the parties shall be determined
by reference to, among other things, whether the untrue or alleged untrue
statement of a material fact or the omission or alleged omission to state a
material fact relates to information supplied by the Company on the one hand or
such Holder or such other indemnified party, as the case may be, on the other,
and the parties' relative intent, knowledge, access to information and
opportunity to correct or prevent such statement or omission. The amount paid by
an indemnified party as a result of the losses, claims, damages or liabilities
referred to in the first sentence of this subsection (d) shall be deemed to
include any legal or other expenses reasonably incurred by such indemnified

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party in connection with investigating or defending any action or claim which is
the subject of this subsection (d). Notwithstanding any other provision of this
Section 4(d), the Holders shall not be required to contribute any amount in
excess of the amount by which the net proceeds received by such Holders from the
sale of the Securities pursuant to the Shelf Registration Statement exceeds the
amount of damages which such Holders have otherwise been required to pay by
reason of such untrue or alleged untrue statement or omission or alleged
omission. No person guilty of fraudulent misrepresentation (within the meaning
of Section 11(f) of the Securities Act) shall be entitled to contribution from
any person who was not guilty of such fraudulent misrepresentation. For purposes
of this paragraph (d), each person, if any, who controls such indemnified party
within the meaning of the Securities Act or the Exchange Act shall have the same
rights to contribution as such indemnified party and each person, if any, who
controls the Company within the meaning of the Securities Act or the Exchange
Act shall have the same rights to contribution as the Company.

                  (e) The agreements contained in this Section 4 shall survive
the sale of the Securities pursuant to the Shelf Registration Statement and
shall remain in full force and effect, regardless of any termination or
cancellation of this Agreement or any investigation made by or on behalf of any
indemnified party.

                  5. ADDITIONAL INTEREST UNDER CERTAIN CIRCUMSTANCES. (a)
Additional interest (the "Additional Interest") with respect to the Notes shall
be assessed as follows if any of the following events occur (each such event in
clauses (i) through (iii) below being herein called a "Registration Default"):

                  (i) the Shelf Registration Statement has not been filed with
         the Commission by the 90th day after the first date of original
         issuance of the Notes;

                  (ii) the Shelf Registration Statement has not been declared
         effective by the Commission by the 150th day after the first date of
         original issuance of the Notes; or

                  (iii) the Shelf Registration Statement is declared effective
         but (A) the Shelf Registration Statement thereafter ceases to be
         effective; or (B) the Shelf Registration Statement or the Prospectus
         ceases to be usable in connection with resales of Transfer Restricted
         Securities (as defined below) during the periods specified herein
         because either (1) any event occurs as a result of which the Prospectus
         forming part of such Shelf Registration Statement would include any
         untrue statement of a material fact or omit to state any material fact
         necessary to make the

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         statements therein in the light of the circumstances under which they
         were made not misleading, or (2) it shall be necessary to amend such
         Shelf Registration Statement or supplement the related prospectus, to
         comply with the Securities Act or the Exchange Act or the respective
         rules thereunder.

                  Additional Interest shall accrue on the Notes over and above
the interest set forth in the title of the Notes from and including the date on
which any such Registration Default shall occur, to but excluding the date on
which all such Registration Defaults have been cured, at a rate of 0.50% per
annum.

                  (b) A Registration Default referred to in Section 5(a)(iii)(B)
shall be deemed not to have occurred and be continuing in relation to the Shelf
Registration Statement or the Prospectus if (i) such Registration Default has
occurred solely as a result of (x) the filing of a post-effective amendment to
the Shelf Registration Statement to incorporate annual audited financial
information with respect to the Company where such post-effective amendment is
not yet effective and needs to be declared effective to permit Holders to use
the related prospectus or (y) other material events, with respect to the Company
that would need to be described in the Shelf Registration Statement or the
related prospectus and (ii) in the case of clause (y), the Company is proceeding
in good faith to amend or supplement the Shelf Registration Statement and
related prospectus to describe such events as required by paragraph 2(h) hereof;
PROVIDED, HOWEVER, that in any case if such Registration Default occurs for a
continuous period in excess of 90 days, Additional Interest shall be payable in
accordance with the above paragraph from the day such Registration Default
occurs until such Registration Default is cured.

                  (c) Any amounts of Additional Interest due pursuant to Section
5(a) will be payable in cash on the regular interest payment dates with respect
to the Notes. The amount of Additional Interest will be determined by
multiplying the applicable Additional Interest rate by the principal amount of
the Notes, further multiplied by a fraction, the numerator of which is the
number of days such Additional Interest rate was applicable during such period
(determined on the basis of a 360- day year comprised of twelve 30-day months),
and the denominator of which is 360. The indebtedness represented by the
Additional Interest shall be subordinated in right of payment to all existing
and future Senior Indebtedness (as defined in the Indenture) as and to the same
extent as the Notes.

                  (d) "Transfer Restricted Securities" means each Security until
(i) the date on which such Security has been effectively registered under the
Securities Act and disposed of

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                                                                            14

in accordance with the Shelf Registration Statement or (ii) the date on which
such Security is distributed to the public pursuant to Rule 144 under the
Securities Act or is saleable pursuant to Rule 144(k) under the Securities Act.

                  6. RULES 144 AND 144A. The Company shall use its best efforts
to file the reports required to be filed by it under the Securities Act and
the Exchange Act in a timely manner and, if at any time the Company is not
required to file such reports, it will, upon the request of any Holder, make
publicly available other information so long as necessary to permit sales of
their securities pursuant to Rules 144 and 144A. The Company covenants that
it will take such further action as any Holder may reasonably request, all to
the extent required from time to time to enable such Holder to sell Transfer
Restricted Securities without registration under the Securities Act within
the limitations of the exemptions provided by Rules 144 and 144A (including
the requirements of Rule 144A(d)(4)). The Company will provide a copy of this
Agreement to prospective purchasers of Securities identified to the Company
by the Initial Purchaser upon request. Upon the request of any Holder, the
Company shall deliver to such Holder a written statement as to whether it has
complied with such requirements. Notwithstanding the foregoing, nothing in
this Section 6 shall be deemed to require the Company to register any of its
securities pursuant to the Exchange Act.

                  7. UNDERWRITTEN REGISTRATIONS. If any of the Transfer
Restricted Securities covered by the Shelf Registration are to be sold in an
underwritten offering, the investment banker or investment bankers and manager
or managers that will administer the offering ("Managing Underwriters") will be
selected by the Company.

                  No person may participate in any underwritten registration
hereunder unless such person (i) agrees to sell such person's Transfer
Restricted Securities on the basis reasonably provided in any underwriting
arrangements approved by the persons entitled hereunder to approve such
arrangements and (ii) completes and executes all questionnaires, powers of
attorney, indemnities, underwriting agreements and other documents reasonably
required under the terms of such underwriting arrangements.

                  8. MISCELLANEOUS. (a) AMENDMENTS AND WAIVERS. The provisions
of this Agreement may not be amended, modified or supplemented, and waivers or
consents to departures from the provisions hereof may not be given, except by
the Company and the written consent of the Holders of a majority in principal
amount of the Securities (provided that Holders of Common Stock issued

<PAGE>

                                                                            15

upon conversion of Notes shall not be deemed Holders of Common Stock, but shall
be deemed to be Holders of the aggregate principal amount of Notes from which
such Common Stock was converted) affected by such amendment, modification,
supplement, waiver or consents.

                  (b) NOTICES. All notices and other communications provided for
or permitted hereunder shall be made in writing by hand delivery, first-class
mail, facsimile transmission, or air courier which guarantees overnight
delivery:

                  (1) if to a Holder, at the most current address given
         by such Holder to the Company;

                  (2) if to the Initial Purchasers:

                       Credit Suisse First Boston Corporation
                       Eleven Madison Avenue
                       New York, NY 10010-3629
                       Fax No.: (212) 325-8278
                       Attention:  Transactions Advisory Group

<PAGE>
                                                                            16

         with a copy to:

                       Cravath, Swaine & Moore
                       Worldwide Plaza
                       825 Eighth Avenue
                       New York, NY 10019
                       Fax No.:  (212) 474-3700
                       Attention:  Kris Heinzelman, Esq.

                  (3) if to the Company, at its address as follows:

                       Affymetrix, Inc.
                       3380 Central Expressway
                       Santa Clara, CA 95051
                       Fax No.: (408) 731-5000
                       Attention: Vernon A. Norviel

         with a copy to:

                       Sullivan & Cromwell
                       1888 Century Park East
                       Los Angles, CA 90067-1725
                       Fax No.: (310) 712-8800
                       Attention: Stanley F. Farrar, Esq.

                  All such notices and communications shall be deemed to have
been duly given: at the time delivered by hand, if personally delivered; three
business days after being deposited in the mail, postage prepaid, if mailed;
when receipt is acknowledged by recipient's facsimile machine operator, if sent
by facsimile transmission; and on the day delivered, if sent by overnight air
courier guaranteeing next day delivery.

                  (c) NO INCONSISTENT AGREEMENTS. The Company has not, as of the
date hereof, entered into, nor shall it, on or after the date hereof, without
the prior consent of CSFBC, enter into, any agreement with respect to its
securities that is inconsistent with the rights granted to the Holders herein or
otherwise conflicts with the provisions hereof.

                  (d)  SUCCESSORS AND ASSIGNS.  This Agreement shall be
binding upon the Company and its successors and assigns.

                  (e) COUNTERPARTS. This Agreement may be executed in any number
of counterparts and by the parties hereto in separate counterparts, each of
which when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement.

<PAGE>
                                                                            17

                  (f) HEADINGS. The headings in this Agreement are for
convenience of reference only and shall not limit or otherwise affect the
meaning hereof.

                  (g) GOVERNING LAW. THIS AGREEMENT SHALL BE GOVERNED BY, AND
CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD
TO PRINCIPLES OF CONFLICTS OF LAWS.

                  By the execution and delivery of this Agreement, the Company
submits to the nonexclusive jurisdiction of any federal or state court in the
State of New York.

                  (h) SEVERABILITY. If any one or more of the provisions
contained herein, or the application thereof in any circumstance, is held
invalid, illegal or unenforceable, the validity, legality and enforceability of
any such provision in every other respect and of the remaining provisions
contained herein shall not be affected or impaired thereby.

                  (i) SECURITIES HELD BY THE COMPANY. Whenever the consent or
approval of Holders of a specified percentage of principal amount of Securities
is required hereunder, Securities held by the Company or its affiliates (other
than subsequent Holders of Securities if such subsequent Holders are deemed to
be affiliates solely by reason of their holdings of such Securities)

<PAGE>

shall not be counted in determining whether such consent or approval was given
by the Holders of such required percentage.

                  If the foregoing is in accordance with your understanding of
our agreement, please sign and return to the Company a counterpart hereof,
whereupon this instrument, along with all counterparts, will become a binding
agreement among the Initial Purchasers and the Company in accordance with its
terms.

                                                 Very truly yours,

                                                 AFFYMETRIX, INC.

                                                 By:______________________
                                                    Name:
                                                    Title:

The foregoing Registration Rights Agreement
is hereby confirmed and accepted
as of the date first above written.

CREDIT SUISSE FIRST BOSTON CORPORATION,
Acting on behalf of themselves
and as The Representative
of the several Initial Purchasers

CREDIT SUISSE FIRST BOSTON CORPORATION,

By:___________________________________
   Name:
   Title:<PAGE>
                                                                  EXHIBIT 10.37

                             RESCISSION AGREEMENT

THIS RESCISSION AGREEMENT is made and entered into by and between PAULA
Insurance Company and Montlake Casualty Company Ltd. (collectively the
"Parties").

WHEREAS, the Parties have previously entered into a workers' compensation
limited risk quota share reinsurance agreement dated November 12, 1999 and
effective July 1, 1999 ("Contract"); and

WHEREAS, the Parties now agree that these reinsurance contracts should be
rescinded and unwound;

NOW THEREFORE, the Parties due hereby represent, covenant and agree that
effective immediately, the Contract will be completely rescinded, released
and canceled as of the inception and in all respects void, and the Parties,
with respect to themselves and with respect to the other, will be treated and
will treat each other as if the Contract had never existed, with no further
obligations whatsoever with respect to the Contract.

IN WITNESS WHEREOF, the Parties have executed this Rescission Agreement by
their duly authorized representatives on the date so indicated:

PAULA INSURANCE COMPANY

By:  /s/ James A. Nicholson       Date 2/10/00
    -----------------------            -------
Name:    James A. Nicholson
Title:   Senior VP/CFO

MONTLAKE CASUALTY COMPANY LTD.

By:  /s/ John R. Snyder           Date 2/11/00
    -------------------                -------
Name:    John R. Snyder
Title:   Treasurer/CFO

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