Exhibit 10.10

                                PROMISSORY NOTE
                                ---------------


$_____________                                          Redwood City, California
                                                        _______________, _______


          _______________, ("Obligor"), for value received, hereby promises to
pay to the order of Maxygen, Inc. or holder ("Payee"), in lawful money of the
United States at the address of Payee set forth below, the principal sum of
_________________________ ($_________.__), together with interest on the unpaid
principal at the compounded annual rate of _____%. Interest shall be due and
payable on December 31 and June 30 of each year. Unpaid principal together with
all accrued interest shall be due and payable on the earlier of (a)
____________, ______ or (b) 30 days after the date of termination of Obligor's
employment by Payee. This Note may be prepaid, in whole or in part, at any time
without premium or penalty.

          If any payment of principal or interest on this Note shall become due
on a Saturday, Sunday, or a public holiday under the laws of the State of
California, such payment shall be made on the next succeeding business day and
such extension of time shall be included in computing interest in connection
with such payment.

          This Note is issued by the Obligor pursuant to, and is subject to, the
terms and conditions of a Stock Purchase Agreement dated ___________, _____ (the
"Agreement"), between Obligor and Payee relating to the sale of Payee's stock to
the Obligor (the "Shares").

          Upon payment in full of all principal and interest payable hereunder,
this Note shall be surrendered to Obligor for cancellation.

          Obligor waives presentment, demand for performance, notice of
nonperformance, protest, notice of protest, and notice of dishonor. No delay on
the part of Payee in exercising any right hereunder shall operate as a waiver of
such right under this Note. This Note is being delivered in and shall be
construed in accordance with the laws of the State of California.

          In the event that Obligor fails to make payment on any date for
payment hereinabove specified of all principal and interest due hereunder on
such date, Obligor shall be deemed to be in default hereunder.  In the event of
such default, Payee may, at Payee's option and in Payee's sole discretion, five
days after giving notice of default to Obligor, accelerate the maturity of all
amounts due under this Note by giving notice of such acceleration.

          If the indebtedness represented by this Note or any part thereof is
collected at law or in equity or in bankruptcy, receivership or other judicial
proceedings or if this Note is placed in the hands of attorneys for collection
after default, Obligor agrees to pay, in addition to the principal and interest
payable hereon, reasonable attorneys' fees and costs incurred by Payee.

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          Any notice or other communication (except payment) required or
permitted hereunder shall be in writing and shall be deemed to have been given
upon delivery if personally delivered or upon deposit if deposited in the United
States mail for mailing by certified mail, postage prepaid, and addressed as
follows:

          If to Payee:
                         Maxygen, Inc.
                         515 Galveston Drive
                         Redwood City, California 94063
                         Attention: President


          If to Obligor:
                         _____________________
                         _____________________
                         _____________________
                         _____________________

          Any payment shall be deemed made upon receipt by Payee. Payee or
Obligor may change their address for purposes of this paragraph by giving to the
other party notice in conformance with this paragraph of such new address.



                                        Obligor:_____________________________

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