EXHIBIT 99.1

                                  CERTIFICATION

     Pursuant  to  Section  906  of  the  Public  Company  Accounting Reform and
Investor Protection 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 certify that, to the best of
their  knowledge:

1.     The Company's Quarterly Report on Form 10-Q for the period ended June 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  and results of operations of the
Company.

IN WITNESS WHEREOF, the undersigned have set their hands hereto as of the 6th
day of August, 2002.



                              /s/  George  A.  Scangos
                              ------------------------
                              CHIEF  EXECUTIVE  OFFICER


                              /s/  Glen  Y.  Sato
                              -------------------
                              CHIEF  FINANCIAL  OFFICER