EXHIBIT 99.1

                    CERTIFICATION OF CEO AND CFO 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 on Form 10-Q of ISP Chemco Inc.
(the "Company") for the quarterly period ended June 30, 2002 as filed with the
Securities and Exchange Commission on the date hereof (the "Report"), Sunil
Kumar, as Chief Executive Officer and President of the Company, and Neal E.
Murphy, as Senior Vice President and Chief Financial Officer of the Company,
each hereby certifies, pursuant to 18 U.S.C. Section 1350, as adopted pursuant
to Section 906 of the Sarbanes-Oxley Act of 2002, that, to the best of his
knowledge and belief:

         (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/ Sunil Kumar
- ----------------------------------------------
Name:  Sunil Kumar
Title: Chief Executive Officer and President

Date:   August 13, 2002



/s/ Neal E. Murphy
- ----------------------------------------------
Name:  Neal E. Murphy
Title: Senior Vice President and
       Chief Financial Officer

Date:   August 13, 2002

This certification accompanies the Report pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002 and shall not, except to the extent required by the
Sarbanes-Oxley Act of 2002, be deemed filed by the Company for purposes of
Section 18 of the Securities Exchange Act of 1934, as amended.