EXHIBIT 1.1

                                 Maxygen, Inc.

                                 Common Stock

                          par value $0.0001 per share

                            Underwriting Agreement
                            ----------------------

                                                                          , 2000


Goldman, Sachs & Co.,
Credit Suisse First Boston Corporation,
FleetBoston Robertson Stephens Inc.,
Invemed Associates LLC,
 As representatives of the several Underwriters
  named in Schedule I hereto,
c/o Goldman, Sachs & Co.
85 Broad Street,
New York, New York 10004.

Ladies and Gentlemen:

  Maxygen, Inc., a Delaware corporation (the "Company"), proposes, subject to
the terms and conditions stated herein, to issue and sell to the Underwriters
named in Schedule I hereto (the "Underwriters") an aggregate of 1,500,000
shares (the "Firm Shares") and, at the election of the Underwriters, up to
225,000 additional shares (the "Optional Shares") of Common Stock, par
value $.0001 ("Stock") of the Company (the Firm Shares and the Optional Shares
that the Underwriters elect to purchase pursuant to Section 2 hereof being
collectively called the "Shares").

  1.      The Company represents and warrants to, and agrees with, each of the
Underwriters that:

  (a)     A registration statement on Form S-1 (File No. 333-[_____]) (the
"Initial Registration Statement") in respect of the Shares has been filed with
the Securities and Exchange Commission (the "Commission"); the Initial
Registration Statement and any post-effective amendment thereto, each in the
form heretofore delivered to you, and, excluding exhibits thereto, to you for
each of the other Underwriters, have been declared effective by the Commission
in such form; other than a registration statement, if any, increasing the size
of the offering (a "Rule 462(b) Registration Statement"), filed pursuant to Rule
462(b) under the Securities Act of 1933, as amended (the "Act"), which became
effective upon filing, no other document with respect to the Initial
Registration Statement has heretofore been filed with the Commission; and no
stop order suspending the effectiveness of the Initial Registration Statement,
any post-effective amendment thereto or the Rule 462(b) Registration Statement,
if any, has been issued and no proceeding for that purpose has been


initiated or threatened by the Commission (any preliminary prospectus included
in the Initial Registration Statement or filed with the Commission pursuant to
Rule 424(a) of the rules and regulations of the Commission under the Act is
hereinafter called a "Preliminary Prospectus"; the various parts of the Initial
Registration Statement and the Rule 462(b) Registration Statement, if any,
including all exhibits thereto and including the information contained in the
form of final prospectus filed with the Commission pursuant to Rule 424(b) under
the Act in accordance with Section 5(a) hereof and deemed by virtue of Rule 430A
under the Act to be part of the Initial Registration Statement at the time it
was declared effective, each as amended at the time such part of the Initial
Registration Statement became effective or such part of the Rule 462(b)
Registration Statement, if any, became or hereafter becomes effective, are
hereinafter collectively called the "Registration Statement"; such final
prospectus, in the form first filed pursuant to Rule 424(b) under the Act, is
hereinafter called the "Prospectus";

  (b)     No order preventing or suspending the use of any Preliminary
Prospectus has been issued by the Commission, and each Preliminary Prospectus,
at the time of filing thereof, conformed in all material respects to the
requirements of the Act and the rules and regulations of the Commission
thereunder, and did not contain an 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 the light of the circumstances under which they were
made, not misleading; provided, however, that this representation and warranty
shall not apply to any statements or omissions made in reliance upon and in
conformity with information furnished in writing to the Company by an
Underwriter through Goldman, Sachs & Co. expressly for use therein;

  (c)     The Registration Statement conforms, and the Prospectus and any
further amendments or supplements to the Registration Statement or the
Prospectus will conform, in all material respects to the requirements of the Act
and the rules and regulations of the Commission thereunder and do not and will
not, as of the applicable effective date as to the Registration Statement and
any amendment thereto, and as of the applicable filing date as to the Prospectus
and any amendment or supplement thereto, contain an 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 not misleading; provided, however, that
this representation and warranty shall not apply to any statements or omissions
made in reliance upon and in conformity with information furnished in writing to
the Company by an Underwriter through Goldman, Sachs & Co. expressly for use
therein;

  (d)     Neither the Company nor any of its subsidiaries has sustained since
the date of the latest audited financial statements included in the Prospectus
any material loss or interference with its business from fire, explosion, flood
or other calamity, whether or not covered by insurance, or from any labor
dispute or court or governmental action, order or decree, otherwise than as set
forth or contemplated in the Prospectus; and, since the respective dates as of
which information is given in the Registration Statement and the Prospectus,
there has not been any change in the capital stock (other than upon the exercise
of options granted pursuant to employee or director stock option plans) or long-
term debt of the Company or any of its subsidiaries or any material adverse
change, or any development involving a prospective material adverse change, in
or affecting the general affairs, management, financial position, stockholders'
equity or results of operations of the Company and its subsidiaries, otherwise
than as set forth or contemplated in the Prospectus;

                                       2


  (e) The Company and its subsidiaries have good and marketable title in fee
simple to all real property and good and marketable title to all personal
property owned by them, in each case free and clear of all liens, encumbrances
and defects except such as are described in the Prospectus or such as do not
materially affect the value of such property and do not materially interfere
with the use made and proposed to be made of such property by the Company and
its subsidiaries; and any real property and buildings held under lease by the
Company and its subsidiaries are held by them under valid, subsisting and
enforceable leases with such exceptions as are not material and do not interfere
with the use made and proposed to be made of such property and buildings by the
Company and its subsidiaries;

  (f) The Company has been duly incorporated and is validly existing as a
corporation in good standing under the laws of Delaware, with power and
authority (corporate and other) to own its properties and conduct its business
as described in the Prospectus, and has been duly qualified as a foreign
corporation for the transaction of business and is in good standing under the
laws of each other jurisdiction in which it owns or leases properties or
conducts any business so as to require such qualification, or is subject to no
material liability or disability by reason of the failure to be so qualified in
any such jurisdiction; and each subsidiary of the Company has been duly
incorporated and is validly existing as a corporation in good standing under the
laws of its jurisdiction of incorporation;

  (g) The Company has an authorized capitalization as set forth in the
Prospectus, and all of the issued shares of capital stock of the Company have
been duly and validly authorized and issued, are fully paid and non-assessable
and conform to the description of the Stock contained in the Prospectus; and all
of the issued shares of capital stock of each subsidiary of the Company have
been duly and validly authorized and issued, are fully paid and non-assessable
and (except for directors' qualifying shares) are owned directly or indirectly
by the Company, free and clear of all liens, encumbrances, equities or claims;

  (h) The unissued Shares to be issued and sold by the Company to the
Underwriters hereunder have been duly and validly authorized and, when issued
and delivered against payment therefor as provided herein, will be duly and
validly issued and fully paid and non-assessable and will conform to the
description of the Stock contained in the Prospectus;

  (i) The issue and sale of the Shares by the Company and the compliance by the
Company with all of the provisions of this Agreement and the consummation of the
transactions herein contemplated will not conflict with or result in a breach or
violation of any of the terms or provisions of, or constitute a default under,
any indenture, mortgage, deed of trust, loan agreement or other material
agreement or material instrument to which the Company or any of its subsidiaries
is a party or by which the Company or any of its subsidiaries is bound or to
which any of the property or assets of the Company or any of its subsidiaries is
subject, nor will such action result in any violation of the provisions of the
Certificate of Incorporation or By-laws of the Company or any statute or any
order, rule or regulation of any court or governmental agency or body having
jurisdiction over the Company or any of its subsidiaries or any of their
properties; and no consent, approval, authorization, order, registration or
qualification of or with any such court or governmental agency or body is
required for the issue and sale of the Shares or the consummation by the Company
of the transactions contemplated by this Agreement, except the registration
under the Act of the Shares and such consents, approvals, authorizations,
registrations or qualifications as may be required under state

                                       3


securities or Blue Sky laws in connection with the purchase and distribution of
the Shares by the Underwriters;

  (j) Neither the Company nor any of its subsidiaries is in violation of its
Certificate of Incorporation or By-laws or in default in the performance or
observance of any material obligation, agreement, covenant or condition
contained in any indenture, mortgage, deed of trust, loan agreement, lease or
other agreement or instrument to which it is a party or by which it or any of
its properties may be bound;

  (k) The statements set forth in the Prospectus under the caption "Description
of Capital Stock", insofar as they purport to constitute a summary of the terms
of the Stock and under the caption "Underwriting", insofar as they purport to
describe the provisions of the laws and documents referred to therein, are
accurate, complete and fair;

  (l) Other than as set forth in the Prospectus, there are no legal or
governmental proceedings pending to which the Company or any of its subsidiaries
is a party or of which any property of the Company or any of its subsidiaries is
the subject which, if determined adversely to the Company or any of its
subsidiaries, would individually or in the aggregate have a material adverse
effect on the current or future consolidated financial position, stockholders'
equity or results of operations of the Company and its subsidiaries; and, to the
best of the Company's knowledge, no such proceedings are threatened or
contemplated by governmental authorities or threatened by others;

  (m) The Company is not and, after giving effect to the offering and sale of
the Shares, will not be an "investment company", as such term is defined in the
Investment Company Act of 1940, as amended (the "Investment Company Act");

  (n) Neither the Company nor any of its affiliates does business with the
government of Cuba or with any person or affiliate located in Cuba within the
meaning of Section 517.075, Florida Statutes;

  (o) Ernst & Young, LLP, who have certified certain financial statements of the
Company and its subsidiaries, are independent public accountants as required by
the Act and the rules and regulations of the Commission thereunder; and

  (p) All of the stockholders listed on Schedule II hereto have delivered
agreements (collectively, the "Lock-up Agreements") that restrict the holders
thereof from, among other things, selling, granting any option for the purchase
of, pledging, or otherwise transferring or disposing of the economic interest
in, any shares of Stock held by such persons, or any securities convertible into
or exercisable or exchangeable for Stock, for a period of 90 days after the date
of the Prospectus without the prior written consent of Goldman, Sachs & Co.,
provided, however, that any shares of Stock purchased by the persons listed in
Schedule II-A hereto in the Company's initial public offering or traded in the
Nasdaq National Market or any other over-the-counter market or stock exchange
are not subject to the foregoing restriction; and the Company has no reason to
believe any Lock-up Agreement is not a valid and binding obligation of each
party thereto other than the Underwriters; and

                                       4


  (q) The Company has imposed a stop-transfer instruction with the Company's
transfer agent in order to enforce the Lock-up Agreements.

  (r) The Company has reviewed its operations and that of its subsidiaries and
any third parties with which the Company or any of its subsidiaries has a
material relationship to evaluate the extent to which the business or operations
of the Company or any of its subsidiaries has been and  will be affected by the
Year 2000 Problem.  As a result of such review, the Company has no reason to
believe, and does not believe, that the Year 2000 Problem has had or will have a
material adverse effect on the general affairs, management, the current or
future consolidated financial position, business prospects, stockholders' equity
or results of operations of the Company and its subsidiaries or result in any
material loss or interference with the Company's business or operations.  The
"Year 2000 Problem" as used herein means any significant risk that computer
hardware or software used in the receipt, transmission, processing,
manipulation, storage, retrieval, retransmission or other utilization of data or
in the operation of mechanical or electrical systems of any kind will not, in
the case of dates or time periods occurring after December 31, 1999, function at
least as effectively as in the case of dates or time periods occurring prior to
January 1, 2000.

  2. Subject to the terms and conditions herein set forth, (a) the Company
agrees to issue and sell to each of the Underwriters, and each of the
Underwriters agrees, severally and not jointly, to purchase from the Company, at
a purchase price per share of $[___], the number of Firm Shares set forth
opposite the name of such Underwriter in Schedule I hereto and (b) in the event
and to the extent that the Underwriters shall exercise the election to purchase
Optional Shares as provided below, the Company agrees to issue and sell to each
of the Underwriters, and each of the Underwriters agrees, severally and not
jointly, to purchase from the Company, at the purchase price per share set forth
in clause (a) of this Section 2, that portion of the number of Optional Shares
as to which such election shall have been exercised (to be adjusted by you so as
to eliminate fractional shares) determined by multiplying such number of
Optional Shares by a fraction, the numerator of which is the maximum number of
Optional Shares which such Underwriter is entitled to purchase as set forth
opposite the name of such Underwriter in Schedule I hereto and the denominator
of which is the maximum number of Optional Shares that all of the Underwriters
are entitled to purchase hereunder.

  The Company hereby grants to the Underwriters the right to purchase at their
election up to 225,000 Optional Shares, at the purchase price per share set
forth in the paragraph above, for the sole purpose of covering sales of shares
in excess of the number of Firm Shares.  Any such election to purchase Optional
Shares may be exercised only by written notice from you to the Company, given
within a period of 30 calendar days after the date of this Agreement, setting
forth the aggregate number of Optional Shares to be purchased and the date on
which such Optional Shares are to be delivered, as determined by you but in no
event earlier than the First Time of Delivery (as defined in Section 4 hereof)
or, unless you and the Company otherwise agree in writing, earlier than two or
later than ten business days after the date of such notice.

  3. Upon the authorization by you of the release of the Firm Shares, the
several Underwriters propose to offer the Firm Shares for sale upon the terms
and conditions set forth in the Prospectus.

                                       5


  4.  (a) The Shares to be purchased by each Underwriter hereunder, in
definitive form, and in such authorized denominations and registered in such
names as Goldman, Sachs & Co. may request upon at least forty-eight hours' prior
notice to the Company shall be delivered by or on behalf of the Company to
Goldman, Sachs & Co., through the facilities of the Depository Trust Company
("DTC"), for the account of such Underwriter, against payment by or on behalf of
such Underwriter of the purchase price therefor by wire transfer of Federal
(same-day) funds to the account specified by the Company to Goldman, Sachs & Co.
at least forty-eight hours in advance. The Company will cause the certificates
representing the Shares to be made available for checking and packaging at least
twenty-four hours prior to the Time of Delivery (as defined below) with respect
thereto at the office of DTC or its designated custodian (the "Designated
Office"). The time and date of such delivery and payment shall be, with respect
to the Firm Shares, 9:30 a.m., New York City time, on [________] or such other
time and date as Goldman, Sachs & Co. and the Company may agree upon in writing,
and, with respect to the Optional Shares, 9:30 a.m., New York time, on the date
specified by Goldman, Sachs & Co. in the written notice given by Goldman, Sachs
& Co. of the Underwriters' election to purchase such Optional Shares, or such
other time and date as Goldman, Sachs & Co. and the Company may agree upon in
writing. Such time and date for delivery of the Firm Shares is herein called the
"First Time of Delivery", such time and date for delivery of the Optional
Shares, if not the First Time of Delivery, is herein called the "Second Time of
Delivery", and each such time and date for delivery is herein called a "Time of
Delivery".

  (b) The documents to be delivered at each Time of Delivery by or on behalf of
the parties hereto pursuant to Section 7 hereof, including the cross receipt for
the Shares and any additional documents requested by the Underwriters pursuant
to Section 7(j) hereof, will be delivered at the offices of Heller Ehrman White
& McAuliffe, 2500 Sand Hill Road, Menlo Park, California, 94025-7063 (the
"Closing Location"), and the Shares will be delivered at the Designated Office,
all at such Time of Delivery.  A meeting will be held at the Closing Location at
1:00 p.m., New York City time, on the New York Business Day next preceding such
Time of Delivery, at which meeting the final drafts of the documents to be
delivered pursuant to the preceding sentence will be available for review by the
parties hereto.  For the purposes of this Section 4, "New York Business Day"
shall mean each Monday, Tuesday, Wednesday, Thursday and Friday which is not a
day on which banking institutions in New York are generally authorized or
obligated by law or executive order to close.

  5.  The Company agrees with each of the Underwriters:

  (a) To prepare the Prospectus in a form approved by you and to file such
Prospectus pursuant to Rule 424(b) under the Act not later than the Commission's
close of business on the second business day following the execution and
delivery of this Agreement, or, if applicable, such earlier time as may be
required by Rule 430A(a)(3) under the Act; to make no further amendment or any
supplement to the Registration Statement or Prospectus which shall be
disapproved by you promptly after reasonable notice thereof; to advise you,
promptly after it receives notice thereof, of the time when any amendment to the
Registration Statement has been filed or becomes effective or any supplement to
the Prospectus or any amended Prospectus has been filed and to furnish you with
copies thereof; to advise you, promptly after it receives notice thereof, of the
issuance by the Commission of any stop order or of any order preventing or
suspending the use of any Preliminary Prospectus or prospectus, of the
suspension of the qualification of the Shares for offering or sale in any
jurisdiction, of the initiation or threatening of any proceeding for any such
purpose, or of any

                                       6


request by the Commission for the amending or supplementing of the Registration
Statement or Prospectus or for additional information; and, in the event of the
issuance of any stop order or of any order preventing or suspending the use of
any Preliminary Prospectus or prospectus or suspending any such qualification,
promptly to use its best efforts to obtain the withdrawal of such order;

  (b) Promptly from time to time to take such action as you may reasonably
request to qualify the Shares for offering and sale under the securities laws of
such jurisdictions as you may request and to comply with such laws so as to
permit the continuance of sales and dealings therein in such jurisdictions for
as long as may be necessary to complete the distribution of the Shares, provided
that in connection therewith the Company shall not be required to qualify as a
foreign corporation or to file a general consent to service of process in any
jurisdiction;

  (c) Prior to 10:00 A.M., New York City time, on the New York Business Day next
succeeding the date of this Agreement and from time to time, to furnish the
Underwriters with copies of the Prospectus in New York City in such quantities
as you may reasonably request, and, if the delivery of a prospectus is required
at any time prior to the expiration of nine months after the time of issue of
the Prospectus in connection with the offering or sale of the Shares and if at
such time any event shall have occurred as a result of which the Prospectus as
then amended or supplemented would include an untrue statement of a material
fact or omit to state any material fact necessary in order to make the
statements therein, in the light of the circumstances under which they were made
when such Prospectus is delivered, not misleading, or, if for any other reason
it shall be necessary during such period to amend or supplement the Prospectus
in order to comply with the Act, to notify you and upon your request to prepare
and furnish without charge to each Underwriter and to any dealer in securities
as many copies as you may from time to time reasonably request of an amended
Prospectus or a supplement to the Prospectus which will correct such statement
or omission or effect such compliance, and in case any Underwriter is required
to deliver a prospectus in connection with sales of any of the Shares at any
time nine months or more after the time of issue of the Prospectus, upon your
request but at the expense of such Underwriter, to prepare and deliver to such
Underwriter as many copies as you may request of an amended or supplemented
Prospectus complying with Section 10(a)(3) of the Act;

  (d) To make generally available to its securityholders as soon as practicable,
but in any event not later than eighteen months after the effective date of the
Registration Statement (as defined in Rule 158(c) under the Act), an earnings
statement of the Company and its subsidiaries (which need not be audited)
complying with Section 11(a) of the Act and the rules and regulations thereunder
(including, at the option of the Company, Rule 158);

  (e) During the period beginning from the date hereof and continuing to and
including the date 90 days after the date of the Prospectus, not to offer, sell,
contract to sell or otherwise dispose of, except as provided hereunder any
securities of the Company that are substantially similar to the Shares,
including but not limited to any securities that are convertible into or
exchangeable for, or that represent the right to receive, Stock or any such
substantially similar securities (other than pursuant to employee, director or
consultant stock option or stock purchase plans existing on, or upon the
conversion or exchange of convertible or exchangeable securities outstanding as
of, the date of this Agreement or in connection with any acquisition
transaction, provided that the recipients of the Company's securities in any
such transaction agree in writing not to offer, sell, contract to sell or
otherwise dispose of such securities during the same 90 day period), without
your prior written consent;

                                       7


  (f) To furnish to its stockholders as soon as practicable after the end of
each fiscal year an annual report (including a balance sheet and statements of
income, stockholders' equity and cash flows of the Company and its consolidated
subsidiaries certified by independent public accountants) and, as soon as
practicable after the end of each of the first three quarters of each fiscal
year (beginning with the fiscal quarter ending after the effective date of the
Registration Statement), to make available to its stockholders consolidated
summary financial information of the Company and its subsidiaries for such
quarter in reasonable detail;

  (g) During a period of five years from the effective date of the Registration
Statement, to furnish to you copies of all reports or other communications
(financial or other) furnished to stockholders, and to deliver to you (i) as
soon as they are available, copies of any reports and financial statements
furnished to or filed with the Commission or any national securities exchange on
which any class of securities of the Company is listed; and (ii) such additional
information concerning the business and financial condition of the Company as
you may from time to time reasonably request (such financial statements to be on
a consolidated basis to the extent the accounts of the Company and its
subsidiaries are consolidated in reports furnished to its stockholders generally
or to the Commission);

  (h) To use the net proceeds received by it from the sale of the Shares
pursuant to this Agreement in the manner specified in the Prospectus under the
caption "Use of Proceeds";

  (i) To use its best efforts to list for quotation the Shares on the National
Association of Securities Dealers Automated Quotations National Market System
("NASDAQ");

  (j) To file with the Commission such information on Form 10-Q or Form 10-K as
may be required by Rule 463 under the Act;

  (k) If the Company elects to rely upon Rule 462(b), the Company shall file a
Rule 462(b) Registration Statement with the Commission in compliance with Rule
462(b) by 10:00 P.M., Washington, D.C. time, on the date of this Agreement, and
the Company shall at the time of filing either pay to the Commission the filing
fee for the Rule 462(b) Registration Statement or give irrevocable instructions
for the payment of such fee pursuant to Rule 111(b) under the Act; and

  (l) The Company will (i) cooperate with the Underwriters to enforce the terms
of each Lock-up Agreement (as defined in Section 1(p)), (ii) issue stop-transfer
instructions to the transfer agent for the Stock with respect to any transaction
or contemplated transaction that would constitute a breach of or default under
the applicable Lock-up Agreement, and (iii) upon written request of Goldman,
Sachs & Co., release from the Lock-up Agreements those shares of Stock held by
those holders set forth in such request. In addition, except with the prior
written consent of Goldman, Sachs & Co., the Company agrees not to amend or
terminate, waive any right under, or consent to any transaction that would
otherwise be prohibited under, any Lock-up Agreement, or take any other action
that would directly or indirectly have the same effect as such an amendment,
termination, waiver or consent; and

  6.  The Company covenants and agrees with the several Underwriters that the
Company will pay or cause to be paid the following: (i) the fees, disbursements
and expenses of the Company's counsel and accountants in connection with the
registration of the Shares under the Act and all other expenses in connection
with the preparation, printing and filing of the Registration Statement, any
Preliminary Prospectus and the Prospectus and amendments and supplements thereto
and the mailing and delivering of copies thereof to the Underwriters and
dealers; (ii) the cost of printing or producing any Agreement among
Underwriters, this Agreement, the Blue Sky Memorandum, closing

                                       8


documents (including any compilations thereof) and any other documents in
connection with the offering, purchase, sale and delivery of the Shares; (iii)
all expenses in connection with the qualification of the Shares for offering and
sale under state securities laws as provided in Section 5(b) hereof, including
the fees and disbursements of counsel for the Underwriters in connection with
such qualification and in connection with the Blue Sky survey (iv) all fees and
expenses in connection with listing the Shares on the NASDAQ; (v) the filing
fees incident to, and the fees and disbursements of counsel for the Underwriters
in connection with, securing any required review by the National Association of
Securities Dealers, Inc. of the terms of the sale of the Shares; (vi) the cost
of preparing stock certificates; (vii) the cost and charges of any transfer
agent or registrar; and (viii) all other costs and expenses incident to the
performance of its obligations hereunder which are not otherwise specifically
provided for in this Section. It is understood, however, that, except as
provided in this Section, and Sections 8 and 11 hereof, the Underwriters will
pay all of their own costs and expenses, including the fees of their counsel,
stock transfer taxes on resale of any of the Shares by them, and any advertising
expenses connected with any offers they may make.

  7.  The obligations of the Underwriters hereunder, as to the Shares to be
delivered at each Time of Delivery, shall be subject, in their discretion, to
the condition that all representations and warranties and other statements of
the Company herein are, at and as of such Time of Delivery, true and correct,
the condition that the Company shall have performed all of its obligations
hereunder theretofore to be performed, and the following additional conditions:

  (a) The Prospectus shall have been filed with the Commission pursuant to Rule
424(b) within the applicable time period prescribed for such filing by the rules
and regulations under the Act and in accordance with Section 5(a) hereof; if the
Company has elected to rely upon Rule 462(b), the Rule 462(b) Registration
Statement shall have become effective by 10:00 P.M., Washington, D.C. time, on
the date of this Agreement; no stop order suspending the effectiveness of the
Registration Statement or any part thereof shall have been issued and no
proceeding for that purpose shall have been initiated or threatened by the
Commission; and all requests for additional information on the part of the
Commission shall have been complied with to your reasonable satisfaction;

  (b) Wilson Sonsini Goodrich & Rosati, Professional Corporation, counsel for
the Underwriters, shall have furnished to you such written opinion or opinions
(a draft of each such opinion is attached as Annex II(a) hereto), dated such
Time of Delivery, with respect to the matters covered in paragraphs (i), (ii),
(vii),  (xiii) and (xiv) of subsection (c) below as well as such other related
matters as you may reasonably request, and such counsel shall have received such
papers and information as they may reasonably request to enable them to pass
upon such matters;

  (c) Heller, Ehrman White & McAuliffe, counsel for the Company, shall have
furnished to you their written opinion (a draft of such opinion is attached as
Annex II(b) hereto), dated such Time of Delivery, in form and substance
satisfactory to you, to the effect that:

      (i)    The Company has been duly incorporated and is validly existing as a
corporation in good standing under the laws of the Delaware with power and
authority (corporate and other) to own its properties and conduct its business
as described in the Prospectus;

      (ii)   The Company has an authorized capitalization as set forth in the
Prospectus, and all of the issued shares of capital stock of the Company
(including the Shares being delivered at such Time of Delivery) have been duly
and validly authorized and issued and are fully paid and non-assessable; and the
Shares conform to the description of the Stock contained in the Prospectus;

                                       9


      (iii)  The Company has been duly qualified as a foreign corporation for
the transaction of business and is in good standing under the laws of each other
jurisdiction in which it owns or leases properties or conducts any business so
as to require such qualification or is subject to no material liability or
disability by reason of failure to be so qualified in any such jurisdiction
(such counsel being entitled to rely in respect of the opinion in this clause
upon opinions of local counsel, published compilations of the laws of such state
and in respect of matters of fact upon certificates of officers of the Company,
provided that such counsel shall state that they believe that both you and they
are justified in relying upon such opinions and certificates);

      (iv)   Each subsidiary of the Company has been duly incorporated and is
validly existing as a corporation in good standing under the laws of its
jurisdiction of incorporation; and all of the issued shares of capital stock of
each such subsidiary have been duly and validly authorized and issued, are fully
paid and non-assessable, and (except for directors' qualifying shares) are owned
directly or indirectly by the Company, free and clear of all liens,
encumbrances, equities or claims (such counsel being entitled to rely in respect
of the opinion in this clause upon opinions of local counsel and in respect to
matters of fact upon certificates of officers of the Company or its
subsidiaries, provided that such counsel shall state that they believe that both
you and they are justified in relying upon such opinions and certificates);

      (v)    The Company and its subsidiaries have good and marketable title in
fee simple to all real property owned by them, in each case free and clear of
all liens, encumbrances and defects except such as (a) are described in the
Prospectus or (b) do not materially affect the value of such property and do not
interfere with the use made and proposed to be made of such property by the
Company and its subsidiaries in a manner that could reasonably be expected to
result in a material adverse change, in the condition, financial or otherwise,
or in the earnings, business, operations or prospects, whether or not arising
from transactions in the ordinary course of business, of the Company and its
subsidiaries, considered as one entity. Any real property and buildings held
under lease by the Company and its subsidiaries are held by them under valid,
subsisting and enforceable leases with such exceptions as are not material and
do not interfere with the use made and proposed to be made of such property and
buildings by the Company and its subsidiaries (in giving the opinion in this
clause, such counsel may state that no examination of record titles for the
purpose of such opinion has been made, and that they are relying upon a general
review of the titles of the Company and its subsidiaries, upon opinions of local
counsel and abstracts, reports and policies of title companies rendered or
issued at or subsequent to the time of acquisition of such property by the
Company or its subsidiaries, upon opinions of counsel to the lessors of such
property and, in respect to matters of fact, upon certificates of officers of
the Company or its subsidiaries, provided that such counsel shall state that
they believe that both you and they are justified in relying upon such opinions,
abstracts, reports, policies and certificates);

      (vi)   To such counsel's knowledge and other than as set forth in the
Prospectus, there are no legal or governmental proceedings pending to which the
Company or any of its subsidiaries is a party or of which any property of the
Company or any of its subsidiaries is the subject and, to such counsel's
knowledge, no such proceedings are threatened or contemplated by governmental
authorities or threatened by others;

      (vii)  This Agreement has been duly authorized, executed and delivered by
the Company;

                                       10


     (viii)  The issue and sale of the Shares being delivered at such Time of
Delivery by the Company and the compliance by the Company with all of the
provisions of this Agreement and the consummation of the transactions herein
contemplated will not conflict with or result in a breach or violation of any of
the terms or provisions of, or constitute a default under, any indenture,
mortgage, deed of trust, loan agreement or other agreement or instrument known
to such counsel to which the Company or any of its subsidiaries is a party or by
which the Company or any of its subsidiaries is bound or to which any of the
property or assets of the Company or any of its subsidiaries is subject, nor
will such action result in any violation of the provisions of the Certificate of
Incorporation or By-laws of the Company or any statute or any order, rule or
regulation known to such counsel of any court or governmental agency or body
having jurisdiction over the Company or any of its subsidiaries or any of their
properties;

     (ix)    No consent, approval, authorization, order, registration or
qualification of or with any such court or governmental agency or body is
required for the issue and sale of the Shares or the consummation by the Company
of the transactions contemplated by this Agreement, except the registration
under the Act of the Shares, and such consents, approvals, authorizations,
registrations or qualifications as may be required under state securities or
Blue Sky laws in connection with the purchase and distribution of the Shares by
the Underwriters;

     (x)     Neither the Company nor any of its subsidiaries is in violation of
its Certificate of Incorporation or By-laws or in default in the performance or
observance of any material obligation, agreement, covenant or condition
contained in any indenture, mortgage, deed of trust, loan agreement, lease or
other agreement or instrument to which it is a party or by which it or any of
its properties may be bound;

     (xi)    The statements set forth in the Prospectus under the caption
"Description of Capital Stock", insofar as they purport to constitute a summary
of the terms of the Stock are accurate, complete and fair;

     (xii)   The Company is not an "investment company", as such term is defined
in the Investment Company Act; and

     (xiii)  The Registration Statement and the Prospectus and any further
amendments and supplements thereto made by the Company prior to such Time of
Delivery (other than the financial statements and related schedules therein, as
to which such counsel need express no opinion) comply as to form in all material
respects with the requirements of the Act and the rules and regulations
thereunder.

     (xiv)   Although they do not assume any responsibility for the accuracy,
completeness or fairness of the statements contained in the Registration
Statement or the Prospectus, except for those referred to in the opinion in
subsection (xi) of this section 7(c), they have no reason to believe that, as of
its effective date, the Registration Statement or any further amendment thereto
made by the Company prior to such Time of Delivery (other than the financial
statements and related schedules therein, as to which such counsel need express
no opinion) contained an untrue statement of a material fact or omitted to state
a material fact required to be stated therein or necessary to make the
statements therein not misleading or that, as of its date, the Prospectus or any
further amendment or supplement thereto made by the Company prior to such Time
of Delivery (other than the financial statements and related schedules therein,
as to which such counsel need express no opinion) contained an untrue statement
of a material fact or omitted to state a material fact necessary

                                       11


to make the statements therein, in the light of the circumstances under which
they were made, not misleading or that, as of such Time of Delivery, either the
Registration Statement or the Prospectus or any further amendment or supplement
thereto made by the Company prior to such Time of Delivery (other than the
financial statements and related schedules therein, as to which such counsel
need express no opinion) contains an untrue statement of a material fact or
omits to state a material fact necessary to make the statements therein, in the
light of the circumstances under which they were made, not misleading; and they
do not know of any amendment to the Registration Statement required to be filed
or of any contracts or other documents of a character required to be filed as an
exhibit to the Registration Statement or required to be described in the
Registration Statement or the Prospectus which are not filed or described as
required;

  (d) On the date of the Prospectus at a time prior to the execution of this
Agreement, at 9:30 a.m., New York City time, on the effective date of any post-
effective amendment to the Registration Statement filed subsequent to the date
of this Agreement and also at each Time of Delivery, Ernst & Young, LLP shall
have furnished to you a letter or letters, dated the respective dates of
delivery thereof, in form and substance satisfactory to you, to the effect set
forth in Annex I hereto (the executed copy of the letter delivered prior to the
execution of this Agreement is attached as Annex I(a) hereto and a draft of the
form of letter to be delivered on the effective date of any post-effective
amendment to the Registration Statement and as of each Time of Delivery is
attached as Annex I(b) hereto);

  (e) (i) Neither the Company nor any of its subsidiaries shall have sustained
since the date of the latest audited financial statements included in the
Prospectus any loss or interference with its business from fire, explosion,
flood or other calamity, whether or not covered by insurance, or from any labor
dispute or court or governmental action, order or decree, otherwise than as set
forth or contemplated in the Prospectus, and (ii) since the respective dates as
of which information is given in the Prospectus there shall not have been any
change in the capital stock or long-term debt of the Company or any of its
subsidiaries or any change, or any development involving a prospective change,
in or affecting the general affairs, management, financial position,
stockholders' equity or results of operations of the Company and its
subsidiaries, otherwise than as set forth or contemplated in the Prospectus, the
effect of which, in any such case described in clause (i) or (ii), is in the
judgment of the Representatives so material and adverse as to make it
impracticable or inadvisable to proceed with the public offering or the delivery
of the Shares being delivered at such Time of Delivery on the terms and in the
manner contemplated in the Prospectus;

  (f) On or after the date hereof (i) no downgrading shall have occurred in the
rating accorded the Company's debt securities, if any, or preferred stock, if
any, by any "nationally recognized statistical rating organization", as that
term is defined by the Commission for purposes of Rule 436(g)(2) under the Act,
and (ii) no such organization shall have publicly announced that it has under
surveillance or review, with possible negative implications, its rating of any
of the Company's debt securities or preferred stock;

  (g) On or after the date hereof there shall not have occurred any of the
following: (i) a suspension or material limitation in trading in securities
generally on the New York Stock Exchange or on NASDAQ; (ii) a suspension or
material limitation in trading in the Company's securities on NASDAQ; (iii) a
general moratorium on commercial banking activities declared by either Federal
or New York or California State authorities; or (iv) the outbreak or escalation
of hostilities involving the United States or the declaration by the United
States of a national emergency or war, if the effect of

                                       12


any such event specified in this clause (iv) in the judgment of the
Representatives makes it impracticable or inadvisable to proceed with the public
offering or the delivery of the Shares being delivered at such Time of Delivery
on the terms and in the manner contemplated in the Prospectus;

  (h) The Shares to be sold at such Time of Delivery shall have been duly listed
for quotation on NASDAQ;

  (i) The Company has obtained and delivered to the Underwriters executed copies
of an agreement from each stockholder listed on Schedule II hereto,
substantially to the effect set forth in Subsection 1(p) hereof in form and
substance satisfactory to you;

  (j) The Company shall have complied with the provisions of Section 5(c) hereof
with respect to the furnishing of prospectuses on the New York Business Day next
succeeding the date of this Agreement; and

  (k) The Company shall have furnished or caused to be furnished to you at such
Time of Delivery certificates of officers of the Company satisfactory to you as
to the accuracy of the representations and warranties of the Company herein at
and as of such Time of Delivery, as to the performance by the Company of all of
its obligations hereunder to be performed at or prior to such Time of Delivery,
as to the matters set forth in subsections (a) and (e) of this Section and as to
such other matters as you may reasonably request.

  (l) Townsend and Townsend and Crew LLP (TTC), special counsel for the Company,
shall have furnished to you its written opinion dated such Time of Delivery, in
form and substance satisfactory to you, to the effect that:

    (i)     To such counsel's knowledge, except as generally described in the
Prospectus, the Company has not received any notice of infringement or of
conflict with rights or claims of others with respect to any intellectual
property, except for an advisory letter from Ixsys Corporation, which TTC
understands has been discussed with you, and with respect to which TTC has
provided opinions of invalidity of the Ixsys patents and noninfringement of the
Company's activities with respect to the Ixsys patents. Except as generally
described in the Prospectus, nothing has come to such counsel's attention that
has led them to believe that any patents of others are infringed by the
processes or practices of the Company, or by the manufacture, use or sale of the
Company's products.

    (ii)    To such counsel's knowledge, except (a) in connection with
assertions or inquiries made by Patent Office examiners in the ordinary course
of the prosecution of the Company's patent applications in the Patent Office and
an opposition in the Australian Patent Office, which TTC understands has been
discussed with you or (b) as may be generally described in the Prospectus, there
is not pending or threatened in writing any action, suit, proceeding or claim
(x) challenging the validity or scope of the patent applications held by or
licensed to the Company or (y) asserting that any patent is infringed by the
processes or practices of the Company, or by the manufacture, use or sale of the
Company's products.

    (iii)   Such counsel, as patent counsel to the Company, except as may be
generally described in the Prospectus, do not know of any pending or threatened
litigation or any governmental proceeding, statute or regulation which would
affect the Company's intellectual property rights to patents or patent
applications, or under any instrument or other document relating thereof.

    (iv)    Such counsel believes that the descriptions relating to patents and
patent applications with respect to all patent matters under "Risk Factors -
Any Inability to Adequately

                                       13


Protect Our Proprietary Technologies Could Harm Our Competitive Position", "Risk
Factors - Litigation or Other Proceedings or Third Party Claims of Intellectual
Property Infringement Could Require Us to Spend Time and Money and Could Shut
Down Some of Our Operations", Business - The Maxygen Solution", "Business -
Maxygen's Molecular Breeding Technologies" and "Business - Intellectual Property
and Technology Licenses" in the Prospectus are accurate and fairly present the
information shown, and such counsel does not know of any instrument or other
document relating to patents or patent applications required to be summarized or
described therein or to be filed as an exhibit thereto which is not so
summarized, described or filed.

    (v)     Such counsel does not believe that the statements relating to
patents, patent applications and patent matters under "Risk Factors - Any
Inability to Adequately Protect Our Proprietary Technologies Could Harm Our
Competitive Position", "Risk Factors - Litigation or Other Proceedings or Third
Party Claims of Intellectual Property Infringement Could Require Us to Spend
Time and Money and Could Shut Down Some of Our Operations", Business - The
Maxygen Solution", "Business - Maxygen's Molecular Breeding Technologies" and
"Business -Intellectual Property and Technology Licenses" in the Registration
Statement such counsel reviewed, contained any untrue statement of a material
fact or omitted to state any material fact which was required to be stated
therein from a patent law perspective or necessary in order to make the
statements therein not misleading.

  8.     (a)  The Company will indemnify and hold harmless each Underwriter
against any losses, claims, damages or liabilities, joint or several, to which
such Underwriter may become subject, under the Act or otherwise, insofar as such
losses, claims, damages or liabilities (or actions in respect thereof) arise out
of or are based upon an untrue statement or alleged untrue statement of a
material fact contained in any Preliminary Prospectus, the Registration
Statement or the Prospectus, or any amendment or supplement thereto, 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 will reimburse each Underwriter for any legal or
other expenses reasonably incurred by such Underwriter in connection with
investigating or defending any such action or claim as such expenses are
incurred; provided, however, that the Company shall not be liable in any such
case to the extent that any such loss, claim, damage or liability arises out of
or is based upon an untrue statement or alleged untrue statement or omission or
alleged omission made in any Preliminary Prospectus, the Registration Statement
or the Prospectus or any such amendment or supplement in reliance upon and in
conformity with written information furnished to the Company by any Underwriter
through Goldman, Sachs & Co. expressly for use therein.

  (b) Each Underwriter will indemnify and hold harmless the Company against any
losses, claims, damages or liabilities to which the Company may become subject,
under the Act or otherwise, insofar as such losses, claims, damages or
liabilities (or actions in respect thereof) arise out of or are based upon an
untrue statement or alleged untrue statement of a material fact contained in any
Preliminary Prospectus, the Registration Statement or the Prospectus, or any
amendment or supplement thereto, 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, in each case
to the extent, but only to the extent, that such untrue statement or alleged
untrue statement or omission or alleged omission was made in any Preliminary
Prospectus, the Registration Statement or the Prospectus or any such amendment
or supplement in reliance upon and in conformity with written information
furnished to the Company by such Underwriter through Goldman, Sachs & Co.
expressly for use therein; and will reimburse the Company for any legal or

                                       14


other expenses reasonably incurred by the Company in connection with
investigating or defending any such action or claim as such expenses are
incurred.

  (c) Promptly after receipt by an indemnified party under subsection (a) or (b)
above of notice of the commencement of any action, such indemnified party shall,
if a claim in respect thereof is to be made against the indemnifying party under
such subsection, notify the indemnifying party in writing of the commencement
thereof; but the omission so to notify the indemnifying party shall not relieve
it from any liability which it may have to any indemnified party otherwise than
under such subsection.  In case any such action shall be brought against any
indemnified party and it shall notify the indemnifying party of the commencement
thereof, the indemnifying party shall be entitled to participate therein and, to
the extent that it shall wish, jointly with any other indemnifying party
similarly notified, to assume the defense thereof, with counsel 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 shall not be liable to such
indemnified party under such subsection for any legal expenses of other counsel
or any other expenses, in each case subsequently incurred by such indemnified
party, in connection with the defense thereof other than reasonable costs of
investigation.  No indemnifying party shall, without the written consent of the
indemnified party, effect the settlement or compromise of, or consent to the
entry of any judgment with respect to, any pending or threatened action or claim
in respect of which indemnification or contribution may be sought hereunder
(whether or not the indemnified party is an actual or potential party to such
action or claim) unless such settlement, compromise or judgment (i) includes an
unconditional release of the indemnified party from all liability arising out of
such action or claim and (ii) does not include a statement as to or an admission
of fault, culpability or a failure to act, by or on behalf of any indemnified
party.

  (d) If the indemnification provided for in this Section 8 is unavailable to or
insufficient to hold harmless an indemnified party under subsection (a) or (b)
above in respect of any losses, claims, damages or liabilities (or actions in
respect thereof) referred to therein, then each indemnifying party shall
contribute to the amount paid or payable by such indemnified party as a result
of such losses, claims, damages or liabilities (or actions in respect thereof)
in such proportion as is appropriate to reflect the relative benefits received
by the Company on the one hand and the Underwriters on the other from the
offering of the Shares.  If, however, the allocation provided by the immediately
preceding sentence is not permitted by applicable law or if the indemnified
party failed to give the notice required under subsection (c) above, then each
indemnifying party shall contribute to such amount paid or payable by such
indemnified party in such proportion as is appropriate to reflect not only such
relative benefits but also the relative fault of the Company on the one hand and
the Underwriters on the other in connection with the statements or omissions
which resulted in such losses, claims, damages or liabilities (or actions in
respect thereof), as well as any other relevant equitable considerations.  The
relative benefits received by the Company on the one hand and the Underwriters
on the other shall be deemed to be in the same proportion as the total net
proceeds from the offering (before deducting expenses) received by the Company
bear to the total underwriting discounts and commissions received by the
Underwriters, in each case as set forth in the table on the cover page of the
Prospectus.  The relative fault 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 the Underwriters on the other and the
parties' relative intent, knowledge, access to information and

                                       15


opportunity to correct or prevent such statement or omission. The Company and
the Underwriters agree that it would not be just and equitable if contributions
pursuant to this subsection (d) were determined by pro rata allocation (even if
the Underwriters were treated as one entity for such purpose) or by any other
method of allocation which does not take account of the equitable considerations
referred to above in this subsection (d). The amount paid or payable by an
indemnified party as a result of the losses, claims, damages or liabilities (or
actions in respect thereof) referred to above in this subsection (d) shall be
deemed to include any legal or other expenses reasonably incurred by such
indemnified party in connection with investigating or defending any such action
or claim. Notwithstanding the provisions of this subsection (d), no Underwriter
shall be required to contribute any amount in excess of the amount by which the
total price at which the Shares underwritten by it and distributed to the public
were offered to the public exceeds the amount of any damages which such
Underwriter has 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 Act)
shall be entitled to contribution from any person who was not guilty of such
fraudulent misrepresentation. The Underwriters' obligations in this subsection
(d) to contribute are several in proportion to their respective underwriting
obligations and not joint.

  (e) The obligations of the Company under this Section 8 shall be in addition
to any liability which the Company may otherwise have and shall extend, upon the
same terms and conditions, to each person, if any, who controls any Underwriter
within the meaning of the Act; and the obligations of the Underwriters under
this Section 8 shall be in addition to any liability which the respective
Underwriters may otherwise have and shall extend, upon the same terms and
conditions, to each officer and director of the Company and to each person, if
any, who controls the Company within the meaning of the Act.

  9.     (a)  If any Underwriter shall default in its obligation to purchase the
Shares which it has agreed to purchase hereunder at a Time of Delivery, you may
in your discretion arrange for you or another party or other parties to purchase
such Shares on the terms contained herein.  If within thirty-six hours after
such default by any Underwriter you do not arrange for the purchase of such
Shares, then the Company shall be entitled to a further period of thirty-six
hours within which to procure another party or other parties satisfactory to you
to purchase such Shares on such terms.  In the event that, within the respective
prescribed periods, you notify the Company that you have so arranged for the
purchase of such Shares, or the Company notifies you that it has so arranged for
the purchase of such Shares, you or the Company shall have the right to postpone
such Time of Delivery for a period of not more than seven days, in order to
effect whatever changes may thereby be made necessary in the Registration
Statement or the Prospectus, or in any other documents or arrangements, and the
Company agrees to file promptly any amendments to the Registration Statement or
the Prospectus which in your opinion may thereby be made necessary. The term
"Underwriter" as used in this Agreement shall include any person substituted
under this Section with like effect as if such person had originally been a
party to this Agreement with respect to such Shares.

  (b) If, after giving effect to any arrangements for the purchase of the Shares
of a defaulting Underwriter or Underwriters by you and the Company as provided
in subsection (a) above, the aggregate number of such Shares which remains
unpurchased does not exceed one-eleventh of the aggregate number of all the
Shares to be purchased at such Time of Delivery, then the Company shall have the
right to require each non-defaulting Underwriter to purchase the number of
shares

                                       16


which such Underwriter agreed to purchase hereunder at such Time of Delivery
and, in addition, to require each non-defaulting Underwriter to purchase its pro
rata share (based on the number of Shares which such Underwriter agreed to
purchase hereunder) of the Shares of such defaulting Underwriter or Underwriters
for which such arrangements have not been made; but nothing herein shall relieve
a defaulting Underwriter from liability for its default.

  (c) If, after giving effect to any arrangements for the purchase of the Shares
of a defaulting Underwriter or Underwriters by you and the Company as provided
in subsection (a) above, the aggregate number of such Shares which remains
unpurchased exceeds one-eleventh of the aggregate number of all the Shares to be
purchased at such Time of Delivery, or if the Company shall not exercise the
right described in subsection (b) above to require non-defaulting Underwriters
to purchase Shares of a defaulting Underwriter or Underwriters, then this
Agreement (or, with respect to the Second Time of Delivery, the obligations of
the Underwriters to purchase and of the Company to sell the Optional Shares)
shall thereupon terminate, without liability on the part of any non-defaulting
Underwriter or the Company, except for the expenses to be borne by the Company
and the Underwriters as provided in Section 6 hereof and the indemnity and
contribution agreements in Section 8 hereof; but nothing herein shall relieve a
defaulting Underwriter from liability for its default.

  10.    The respective indemnities, agreements, representations, warranties and
other statements of the Company and the several Underwriters, as set forth in
this Agreement or made by or on behalf of them, respectively, pursuant to this
Agreement, shall remain in full force and effect, regardless of any
investigation (or any statement as to the results thereof) made by or on behalf
of any Underwriter or any controlling person of any Underwriter, or the Company,
or any officer or director or controlling person of the Company, and shall
survive delivery of and payment for the Shares.

  11.    If this Agreement shall be terminated pursuant to Section 9 hereof, the
Company shall not then be under any liability to any Underwriter except as
provided in Sections 6 and 8 hereof; but, if for any other reason, any Shares
are not delivered by or on behalf of the Company as provided herein, the Company
will reimburse the Underwriters through you for all out-of-pocket expenses
approved in writing by you, including fees and disbursements of counsel,
reasonably incurred by the Underwriters in making preparations for the purchase,
sale and delivery of the Shares not so delivered, but the Company shall then be
under no further liability to any Underwriter except as provided in Sections 6
and 8 hereof.

  12.    In all dealings hereunder, you shall act on behalf of each of the
Underwriters, and the parties hereto shall be entitled to act and rely upon any
statement, request, notice or agreement on behalf of any Underwriter made or
given by you jointly or by Goldman, Sachs & Co. on behalf of you as the
representatives.

  All statements, requests, notices and agreements hereunder shall be in
writing, and if to the Underwriters shall be delivered or sent by mail, telex or
facsimile transmission to you as the representatives in care of Goldman, Sachs &
Co., 32 Old Slip, 21st Floor, New York, New York  10005, Attention: Registration
Department; and if to the Company shall be delivered or sent by mail to the
address of the Company set forth in the Registration Statement, Attention:
Secretary; provided, however, that any notice to an Underwriter pursuant to
Section 8(c) hereof shall be delivered or sent by mail, telex or facsimile
transmission to such Underwriter at its address set forth in its Underwriters'
Questionnaire, or telex constituting such Questionnaire, which address will be
supplied to the

                                       17


Company by you upon request. Any such statements, requests, notices or
agreements shall take effect upon receipt thereof.

  13.    This Agreement shall be binding upon, and inure solely to the benefit
of, the Underwriters, the Company and, to the extent provided in Sections 8 and
10 hereof, the officers and directors of the Company and each person who
controls the Company or any Underwriter, and their respective heirs, executors,
administrators, successors and assigns, and no other person shall acquire or
have any right under or by virtue of this Agreement. No purchaser of any of the
Shares from any Underwriter shall be deemed a successor or assign by reason
merely of such purchase.

  14.    Time shall be of the essence of this Agreement.  As used herein, the
term "business day" shall mean any day when the Commission's office in
Washington, D.C. is open for business.

  15.    This Agreement shall be governed by and construed in accordance with
the laws of the State of New York.

  16.    This Agreement may be executed by any one or more of the parties hereto
in any number of counterparts, each of which shall be deemed to be an original,
but all such counterparts shall together constitute one and the same instrument.

                                       18


  If the foregoing is in accordance with your understanding, please sign and
return to us seven (7) counterparts hereof, and upon the acceptance hereof by
you, on behalf of each of the Underwriters, this letter and such acceptance
hereof shall constitute a binding agreement between each of the Underwriters and
the Company.  It is understood that your acceptance of this letter on behalf of
each of the Underwriters is pursuant to the authority set forth in a form of
Agreement among Underwriters, the form of which shall be submitted to the
Company for examination upon request, but without warranty on your part as to
the authority of the signers thereof.

                                       Very truly yours,

                                       Maxygen, Inc.

                                       By: ____________________________________
                                           Name:
                                           Title:

Accepted as of the date hereof:

Goldman, Sachs & Co.
Credit Suisse First Boston Corporation
FleetBoston Robertson Stephens Inc.
Invemed Associates LLC

By: __________________________________
          Goldman, Sachs & Co.

 On behalf of each of the Underwriters

                                       19




- -------------------------------------------------------------------------------------------------------------------
                                                        SCHEDULE I
- -------------------------------------------------------------------------------------------------------------------
                                                                                                 Number of Optional
- -------------------------------------------------------------------------------------------------------------------
                                                                                                    Shares to be
- -------------------------------------------------------------------------------------------------------------------
                                                                     Total Number of                Purchased if
- -------------------------------------------------------------------------------------------------------------------
                                                                       Firm Shares                 Maximum Option
- -------------------------------------------------------------------------------------------------------------------
                      Underwriter                                     to be Purchased                 Exercised
                      -----------                                    ---------------               --------------
- -------------------------------------------------------------------------------------------------------------------
                                                                                           
Goldman, Sachs & Co...........................................
- -------------------------------------------------------------------------------------------------------------------
Credit Suisse First Boston Corporation........................
- -------------------------------------------------------------------------------------------------------------------
FleetBoston Robertson Stephens Inc............................
- -------------------------------------------------------------------------------------------------------------------
Invemed Associates LLC........................................
- -------------------------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------------------------
        Total.................................................
- -------------------------------------------------------------------------------------------------------------------


                                       20


                                  SCHEDULE II

Schedule IIA:
Russell J. Howard
Russell and Maureen Howard Trust
Simba Gill
Michael Rabson
Willem P.C. Stemmer
John Bedbrook
Howard A. Simon
Norman Kruse
Isaac Stein
Stein 1995 Revocable Trust
Stein Partners
Robert J. Glaser
M.R.C. Greenwood
Adrian Hennah
Gordon Ringold
Gregory Zarucki Ringold 1998 Trust
Alexander Zarucki Ringold 1998 Trust
Melanie Gault-Ringold 1998 Trust
George Poste
Julian N. Stern
Glaxo Wellcome International BV
Glaxo Wellcome plc
Technogen Associates, L.P.
Technogen Enterprises, L.L.C.
Lombard Odier & Cie

Schedule IIB:
R.A. Investment Group and Affiliates
R.A. Investment Group
Pioneer Hi-Bred International
Pioneer Overseas Corporation
Alejandro Zaffaroni
Zaffaroni Family Partnership L.P.
Zaffaroni Revocable Trust 1/24/86
Alejandro & Lida Zaffroni Revoc. Trust UTA 1-24-86
Elisa Zaffaroni Trust UTA 4-15-89
Charles Adam Zaffaroni Trust UTD 12/29/88
Alexander Peter Zaffaroni Trust UTD 12/29/88
The Zaffaroni Family Partnership L.P.
Alexander Peter Zaffaroni Trust UTD 04/15/89
Charles Adam Zaffaroni Trust UTD 04/15/89
Miller Family Investors, L.L.C.
Jerry Cohn
[Other Directed Share Purchasers Allocated Shares by Dr. Zaffaroni and R.A.
Investment Group]

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