PRUDENTIAL UNIT TRUSTS TAX EXEMPT SERIES 21, 497J, 1995-09-01

PRUDENTIAL UNIT TRUSTS TAX EXEMPT SERIES 21
497J, 1995-09-01

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                              Rule 497(j)
                              Registration No. 33-11297


Pursuant to Rule 497(j) promulgated under the Securities Act of
1933, the Registrant, Prudential Unit Trusts, Tax-Exempt
Series 21 and Insured Tax-Exempt Series 25 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 21  
                         Insured Tax-Exempt Series 25


                         By: Prudential Securities Incorporated
                                  (Depositor)


                             Richard R. Hoffmann
                             Richard R. Hoffmann
                             Authorized Signatory