Executed in 6 Parts
                                             Counterpart No. (   )



                              NATIONAL EQUITY TRUST
                           OTC Growth Trust Series 21
                            REFERENCE TRUST AGREEMENT



     This  Reference  Trust  Agreement  dated  ________,  2002 among  Prudential
Investment  Management  Services  LLC, as  Depositor,  The Bank of New York,  as
Trustee and Prudential  Securities  Incorporated,  as Portfolio  Supervisor sets
forth certain  provisions in full and incorporates other provisions by reference
to the document entitled  "National Equity Trust, Trust Indenture and Agreement"
(the "Basic Agreement") dated February 2, 2000. Such provisions as are set forth
in full herein and such provisions as are incorporated by reference constitute a
single instrument (the "Indenture").


                                WITNESSETH THAT:


     In  consideration  of the  premises  and of the  mutual  agreements  herein
contained, the Depositor and the Trustee agree as follows: Part I.

                     STANDARD TERMS AND CONDITIONS OF TRUST


     Subject to the provisions of Part II hereof,  all the provisions  contained
in the Basic  Agreement are herein  incorporated  by reference in their entirety
and  shall be deemed  to be a part of this  instrument  as fully and to the same
extent as though said provisions had been set forth in full in this instrument.


A.   Article I, entitled "Definitions," shall be amended as follows:

(i)  Section  1.01-Definitions  shall be amended to add the following definition
     at the end thereof:

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     "Portfolio  Supervisor" of the Trust shall have the meaning  assigned to it
in Part II of the Reference Trust Agreement.

B.   Article  III,  entitled  "Administration  of  Trust,"  shall be  amended as
     follows:

     (i) The third  paragraph of Section  3.05-Distribution  shall be amended by
deleting any reference to Depositor and replacing it with Portfolio Supervisor.

     (ii)  Section  3.14-Deferred  Sales  Charge  shall  be  amended  to add the
following sentences at the end thereof:

"References to Deferred Sales Charge in this Trust Indenture and Agreement shall
include any Creation and  Development  Fee  indicated  in the  prospectus  for a
Trust.  The  Creation  and  Development  Fee  shall be  payable  on each date so
designated  and in an amount  determined  as specified in the  prospectus  for a
Trust."


C.   Article VIII, entitled "Depositor," shall be amended as follows:


     (i) Section 8.07-Compensation shall be amended by deleting any reference to
Depositor and replacing it with Portfolio Supervisor.


D.   Article IX,  entitled  "Additional  Covenants;  Miscellaneous  Provisions,"
     shall be amended as follows:


     (i) The first sentence of Section 9.05 - Written Notice shall be amended by
deleting the language "Prudential Securities  Incorporated at One Seaport Plaza,
New  York,  New  York  10292"  and  replacing  it  with  "Prudential  Investment
Management LLC at 100 Mulberry Street,  Gateway Center Three, Newark, New Jersey
07102".


                                    Part II.

                     SPECIAL TERMS AND CONDITIONS OF TRUST


     The following special terms and conditions are hereby agreed to:


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A.   The Trust is denominated National Equity Trust, OTC Growth Trust Series 21.

B.   The Units of the Trust shall be subject to a deferred sales charge.

C.   The publicly traded stocks listed in Schedule A hereto are those which,
     subject to the terms of this Indenture, have been or are to be deposited in
     Trust under this Indenture as of the date hereof.

D.   The term "Depositor" shall mean Prudential  Investment  Management Services
     LLC.

E.   The  term  "Portfolio   Supervisor"   shall  mean   Prudential   Securities
     Incorporated.

F.   The aggregate number of Units referred to in Sections 2.03 and 9.01 of the
      Basic Agreement is          as of the date hereof.

G.   A Unit of the Trust is hereby declared initially equal to 1/     th of the
     Trust.

H.   The term "First Settlement Date" shall mean                        , 2002.

I.   The terms "Computation Day" and "Record Date" shall be on such dates as the
     Sponsor shall direct.


J.   The term  "Distribution  Date" shall be on such dates as the Sponsor  shall
     direct.

K.   The term "Termination Date" shall mean          , 2003.

L.   The Trustee's Annual Fee shall be $.90 (per 1,000 Units) for 49,999,999 and
     below  units  outstanding  $.84 (per  1,000  Units) on the next  50,000,000
     Units,  $.78 (per 1,000 Units) on the next 100,000,000  Units and $.66 (per
     1,000 Units) on Units in excess of 200,000,000  Units.  In calculating  the
     Trustee's annual fee, the fee applicable to the number of units outstanding
     shall apply to all units outstanding.

M.   The Depositor's  Portfolio  supervisory service fee shall be $.25 per 1,000
     Units.



               [Signatures and acknowledgments on separate pages]