Exhibit 99.1



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


     In connection  with the Quarterly  Report of UnionBanCal  Corporation  (the
"Company")  on Form 10-Q for the period  ending March 31, 2003 as filed with the
Securities  and  Exchange  Commission  on the date  hereof  (the  "Report"),  I,
Norimichi Kanari, Chief Executive Officer of the Company,  certify,  pursuant to
18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley
Act of 2002, that, to my knowledge:

     (1) The Report fully  complies  with the  requirements  of Section 13(a) or
         15(d) of the Securities Exchange Act of 1934; and

     (2)  The  information  contained  in the  Report  fairly  presents,  in all
material  respects,  the  financial  condition  and results of operations of the
Company.



Dated:  May 14, 2003
      -------------------



                             By:    /s/ NORIMICHI KANARI
                                ---------------------------------
                                        Norimichi Kanari
                                    Chief Executive Officer


     A signed  original of this  written  statement  required by Section 906 has
been provided to  UnionBanCal  Corporation  and will be retained by  UnionBanCal
Corporation and furnished to the Securities and Exchange Commission or its staff
upon request.