Exhibit 99.1

                          ISP CHEMCO INC. [Letterhead]



March 26, 2002

Securities and Exchange Commission
450 Fifth Street, N.W.
Washington, D.C. 20549-0408

Re: LETTER TO COMMISSION PURSUANT TO TEMPORARY NOTE 3T

Ladies and Gentlemen:

Pursuant to Temporary Note 3T to Article 3 of Regulation S-X, ISP Chemco Inc.
has obtained a letter of representation from Arthur Andersen LLP ("Andersen")
stating that the December 31, 2001 audit was subject to their quality control
system for the U.S. accounting and auditing practice to provide reasonable
assurance that the engagement was conducted in compliance with professional
standards, that there was appropriate continuity of Andersen personnel working
on the audit, availability of national office consultation and availability of
personnel at foreign affiliates of Andersen to conduct the relevant portions of
the audit.

Very truly yours,

ISP Chemco Inc.

/s/ Neal E. Murphy

Neal E. Murphy
Senior Vice President and
Chief Financial Officer