HERCULES INCORPORATED

                                                                    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 Annual Report of Hercules Incorporated (the
"Company") on Form 10-K for the period ended December 31, 2002 as filed with the
Securities and Exchange Commission on the date hereof (the "Report"), I, William
H. Joyce, 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.

/s/ William H. Joyce
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William H. Joyce
Chief Executive Officer
March 31, 2003

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