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 Quarterly Report of Hercules Incorporated (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, William H. Joyce,
Chairman and 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
- ------------------------------------
William H. Joyce
Chairman and Chief Executive Officer
May 15, 2003

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


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