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Rule 497(j)
Registration No. 33-9340
Registration No. 33-7345
Pursuant to Rule 497(j) promulgated under the Securities Act of
1933, the Registrant, Prudential Unit Trusts, Tax-Exempt Series
18 and Insured Tax-Exempt Series 21 hereby certifies as follows:
1) the form of prospectus that would have been filed under
paragraph (b) of Rule 497 does not differ from that contained in
the most recent amendment to the registration statement, and
2) the text of the said amendment to the registration statement
has been filed electronically.
PRUDENTIAL UNIT TRUSTS,
Tax-Exempt Series 18
Insured Tax-Exempt Series 21
By: Prudential Securities Incorporated
(Depositor)
Richard R. Hoffmann
Richard R. Hoffmann
Authorized Signatory