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                                                                   Exhibit 10.4

                                 PROMISSORY NOTE
                                     (Exim)

$10,000,000.00                                                 January 30, 2003

         FOR VALUE RECEIVED, the undersigned (jointly and severally,
individually and collectively, the "Borrower"), jointly and severally promises
to pay to the order of Silicon Valley Bank ("Bank"), at such place as the holder
hereof may designate, in lawful money of the United States of America, the
aggregate unpaid principal amount of all advances ("Advances") made by Bank to
Borrower, up to a maximum principal amount of Ten Million Dollars
($10,000,000.00), plus interest on the aggregate unpaid principal amount of such
Advances, at the rates and in accordance with the terms of the Export-Import
Bank Loan and Security Agreement between Borrower and Bank of even date
herewith, as amended from time to time (the "Loan Agreement") on the first
calendar day of each month after an Advance has been made. The entire principal
amount and all accrued interest shall be due and payable on January 29, 2005, or
on such earlier date, as provided for in the Loan Agreement.

         Borrower irrevocably waives the right to direct the application of any
and all payments at any time hereafter received by Bank from or on behalf of
Borrower, and Borrower irrevocably agrees that Bank shall have the continuing
exclusive right to apply any and all such payments against the then due and
owing obligations of Borrower as Bank may deem advisable. In the absence of a
specific determination by Bank with respect thereto, all payments shall be
applied in the following order: (a) then due and payable fees and expenses; (b)
then due and payable interest payments and mandatory prepayments; and (c) then
due and payable principal payments and optional prepayments.

         Bank is hereby authorized by Borrower to endorse on Bank's books and
records each Advance made by Bank under this Note and the amount of each payment
or prepayment of principal of each such Advance received by Bank; it being
understood, however, that failure to make any such endorsement (or any errors in
notation) shall not affect the obligations of Borrower with respect to Advances
made hereunder, and payments of principal by Borrower shall be credited to
Borrower notwithstanding the failure to make a notation (or any errors in
notation) thereof on such books and records.

         Borrower promises to pay Bank all reasonable costs and reasonable
expenses including all reasonable attorneys' fees, incurred in such collection
or in any suit or action to collect this Note or in any appeal thereof, unless a
final court of competent jurisdiction finds that the Bank acted with gross
negligence or willful misconduct. Borrower waives presentment, demand, protest,
notice of protest, notice of dishonor, notice of nonpayment, and any and all
other notices and demands in connection with the delivery, acceptance,
performance, default or enforcement of this Note, as well as any applicable
statute of limitations. No delay by Bank in exercising any power or right
hereunder shall operate as a waiver of any power or right. Time is of the
essence as to all obligations hereunder.

         This Note is issued pursuant to the Loan Agreement, which shall govern
the rights and obligations of Borrower with respect to all obligations
hereunder.

         The law of the Commonwealth of Massachusetts shall apply to this
Agreement. BORROWER AND BANK EACH ACCEPTS FOR ITSELF AND IN CONNECTION WITH ITS
PROPERTIES, UNCONDITIONALLY, THE NON-EXCLUSIVE JURISDICTION OF ANY STATE OR
FEDERAL COURT OF COMPETENT JURISDICTION IN THE COMMONWEALTH OF MASSACHUSETTS IN
ANY ACTION, SUIT, OR PROCEEDING OF ANY KIND, AGAINST IT WHICH ARISES OUT OF OR
BY REASON OF THIS NOTE OR THE LOAN AGREEMENT; PROVIDED, HOWEVER, THAT IF FOR ANY
REASON BANK CANNOT AVAIL ITSELF OF THE COURTS OF THE COMMONWEALTH OF
MASSACHUSETTS, BORROWER ACCEPTS JURISDICTION OF THE COURTS AND VENUE IN SANTA
CLARA COUNTY, CALIFORNIA.

         BORROWER WAIVES ITS RIGHT TO A JURY TRIAL OF ANY CLAIM OR CAUSE OF
ACTION

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BASED UPON OR ARISING OUT OF ANY OF THE EXIM LOAN DOCUMENTS OR ANY OF THE
TRANSACTIONS CONTEMPLATED THEREIN, INCLUDING CONTRACT CLAIMS, TORT CLAIMS,
BREACH OF DUTY CLAIMS, AND ALL OTHER COMMON LAW OR STATUTORY CLAIMS. BORROWER
RECOGNIZES AND AGREES THAT THE FOREGOING WAIVER CONSTITUTES A MATERIAL
INDUCEMENT FOR IT TO ENTER INTO THIS AGREEMENT. BORROWER REPRESENTS AND WARRANTS
THAT IT HAS REVIEWED THIS WAIVER WITH ITS LEGAL COUNSEL AND THAT IT KNOWINGLY
AND VOLUNTARILY WAIVES ITS JURY TRIAL RIGHTS FOLLOWING CONSULTATION WITH LEGAL
COUNSEL.

                                   ASPEN TECHNOLOGY, INC.

                                   By: /s/ Lisa W. Zappala
                                       ----------------------------------------
                                   Name: Lisa W. Zappala
                                   Title: Senior Vice President and
                                          Chief Financial Officer

                                   ASPENTECH, INC.

                                   By: /s/ Lisa W. Zappala
                                       ----------------------------------------
                                       Name: Lisa W. Zappala
                                       Title:  Treasurer