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 September 29, 2002 as filed with
the Securities and Exchange Commission on the date hereof (the "Report"),  Sunil
Kumar,  as President  and Chief  Executive  Officer 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:   President and Chief Executive Officer

Date:   November 13, 2002



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

Date:   November 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.