REICH & TANG DISTRIBUTORS L.P.
600 Fifth Avenue
New York, New York 10020
(212) 830-5400
December 5, 1997
VIA EDGAR
Securities and Exchange Commission
450 Fifth Street, N.W.
Washington, D.C. 20549
Re: Insured Municipal Securities Trust, Series 21
File No. 33-28702
Gentlemen:
As Sponsors of the above-referenced Trust, we are writing this
letter to certify that:
(1) the form of Prospectus that would have been filed under
Rule 497(b) of the Securities Act of 1933, does not differ from that contained
in the most recent Post-Effective Amendment to the Registration Statement on
Form S-6 (the "Registration Statement"), and
(2) the text of the most recent Registration Statement was
filed electronically with the Securities and Exchange Commission on October 29,
1997 and became effective October 31, 1997 pursuant to Rule 485(b).
Insured Municipal Securities Trust, Series 21
REICH & TANG DISTRIBUTORS L.P.
GRUNTAL & CO., L.L.C.
By:
-------------------------------------
Peter J. DeMarco
as agent for the Sponsors
659792.1
