Aspen Technology 10-K 2006 FY Annual report

Exhibit 32.1

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350,
AS ADOPTED PURSUANT TO
SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Annual Report on Form 10-K of Aspen Technology, Inc. (the “Company”) for the period ended June 30, 2006 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), the undersigned, Mark E. Fusco, President and Chief Executive Officer of the Company, hereby certifies, pursuant to 18 U.S.C. Section 1350, that:

(1)  The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2)  The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Dated: September 28, 2006	/s/ Mark E. Fusco
	Mark E. Fusco President and Chief Executive Officer (Principal Executive Officer)