1 As filed with the Securities and Exchange Commission on June 17, 1999 Registration No. 333-61121 ================================================================================ 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 ================================================================================

2 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 333-61121) and not sold as of the time of filing of this Post-Effective Amendment No. 1.

3 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