June 28, 2000



Securities and Exchange Commission

450 Fifth Street, N.W.

Washington, D.C.  20549

Attn:  Filing Desk



To Whom It May Concern:



By means of this letter I authorize Michael Rabson and Paul Quinlan, or

either of them individually, to sign on my behalf all forms required

under Section 16(a) of the Securities Exchange Act of 1934, as amended,

relating to transactions involving the stock or derivative securities

of Maxygen, Inc. (the "Company").  Either such individual is

accordingly authorized to sign any Form 3, Form 4, Form 5 or amendment

thereto that I am required to file with the same effect as if I had

signed them myself.



This authorization shall remain in effect until revoked in writing by

me.



Yours truly,



/s/ Gordon Ringold