EXHIBIT 99.1



      CERTIFICATION OF CHIEF EXECUTIVE OFFICER AND CHIEF FINANCIAL OFFICER
                                   PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002



        I, Scott G. McNealy, certify, pursuant to 18 U.S.C. Section 1350, as
adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the
Quarterly Report of Sun Microsystems, Inc. on Form 10-Q for the quarterly period
ended December 29, 2002 fully complies with the requirements of Section 13(a)
or 15(d) of the Securities Exchange Act of 1934 and that information contained
in such Quarterly Report on Form 10-Q fairly presents in all material respects
the financial condition and results of operations of Sun Microsystems, Inc.




                                             By:    /s/ Scott G. McNealy
                                                 -------------------------------

                                             Name:  Scott G. McNealy
                                             Title: Chief Executive Officer