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      As filed with the Securities and Exchange Commission on June 17, 1999

                                                     Registration No. 333-57295
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                              -------------------


                         POST-EFFECTIVE AMENDMENT NO. 1
                                       TO
                                    FORM S-3
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                              -------------------


                             ASPEN TECHNOLOGY, INC.
             (Exact name of registrant as specified in its charter)





          DELAWARE                                              04-2739697
(State or other jurisdiction                                 (I.R.S. employer
of incorporation or organization)                         identification number)






                                 Ten Canal Park
                         Cambridge, Massachusetts 02141
                                 (617) 949-1000

(Address, including zip code, and telephone number, including area code, of
 registrant's principal executive offices)

                              -------------------


                                Lawrence B. Evans
                Chairman of the Board and Chief Executive Officer
                             ASPEN TECHNOLOGY, INC.
                                 Ten Canal Park
                         Cambridge, Massachusetts 02141
                                 (617) 949-1000
(Name, address, including zip code, and telephone number, including area
code, of agent for service)

                              -------------------


                                   Copies to:


   Stephen J. Doyle, Esq.                               Mark L. Johnson, Esq.
Vice President, General Counsel,                      FOLEY, HOAG & ELIOT LLP
Chief Legal Officer and Secretary                      One Post Office Square
      ASPEN TECHNOLOGY, INC.                         Boston, Massachusetts 02109
          Ten Canal Park
  Cambridge, Massachusetts 02141


================================================================================




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      The Registrant hereby withdraws from registration all of those shares of
its common stock, $.10 par value per share, registered pursuant to its
Registration Statement on Form S-3 (registration number 333-57295) and not sold
as of the time of filing of this Post-Effective Amendment No. 1.


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                                   SIGNATURES

      Pursuant to the requirements of the Securities Act of 1933, the Registrant
has duly caused this Post-Effective Amendment No. 1 to Registration Statement to
be signed on its behalf by the undersigned, thereunto duly authorized, in the
City of Cambridge, Massachusetts, as of June 17, 1999.

                                                 ASPEN TECHNOLOGY, INC.


                                                 By: /s/ LAWRENCE B. EVANS
                                                    ----------------------
                                                    Lawrence B. Evans
                                                    Chairman of the Board and
                                                    Chief Executive Officer

      Pursuant to the requirements of the Securities Act of 1933, this
Post-Effective Amendment No. 1 to Registration Statement has been signed below
by the following persons in the capacities indicated as of June 17, 1999.
SIGNATURE TITLE --------- ----- /s/ LAWRENCE B. EVANS Chairman of the Board and Chief Executive Officer - ----------------------- (Principal Executive Officer) Lawrence B. Evans * Chief Financial Officer (Principal Financial and - ----------------------- Accounting Officer) Lisa W. Zappala * Director - ----------------------- Joseph F. Boston * Director - ----------------------- Gresham T. Brebach, Jr. * Director - ----------------------- Douglas R. Brown * Director - ----------------------- Joan C. McArdle * Director - ----------------------- Alison Ross *By /s/ LAWRENCE B. EVANS ---------------------- Lawrence B. Evans Attorney-in-fact