Exhibit 99.1
                                                                    ------------

                                  CERTIFICATION

Pursuant  to Section 906 of the Sarbanes-Oxley Act of 2002 (18 U.S.C.   1350, as
adopted),  George  A.  Scangos,  Chief  Executive Officer of Exelixis, Inc. (the
"Company"),  and  Glen  Y.  Sato,  Chief  Financial Officer of the Company, each
hereby  certifies  that,  to  his  knowledge:

1.     The  Company's  Quarterly  Report  on  Form  10-Q  for  the  period ended
September  30, 2002, and to which this Certification is attached as Exhibit 99.1
(the  "Periodic  Report"), fully complies with the requirements of section 13(a)
or  section  15(d)  of  the  Securities  Exchange  Act  of  1934,  and

2.     The  information contained in the Periodic Report fairly presents, in all
material  respects,  the  financial  condition  of the Company at the end of the
periods  covered  by  the  Periodic  Report and the results of operations of the
Company  for  the  periods  covered  by  the  Periodic  Report.

This  certification  accompanies  the Periodic Report pursuant to Section 906 of
the  Sarbanes-Oxley  Act  of 2002 and shall not be deemed "filed" by the Company
for  purposes  of Section 18 of the Securities Exchange Act of 1934, as amended.


     Dated:  November  7,  2002



                              /s/  George  A.  Scangos
                              -----------------------------------------------
                              GEORGE  A.  SCANGOS,  CHIEF  EXECUTIVE  OFFICER


                              /s/  Glen  Y.  Sato
                              -----------------------------------------------
                              GLEN  Y.  SATO,  CHIEF  FINANCIAL  OFFICER