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  First  Financial  Bancorp  (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, Leon
Zimmerman,  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:

         (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.


May 12, 2003                                         /s/Leon Zimmerman
                                                     ------------------
                                                     Chief Executive Officer



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

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