Room 4561
via fax (617) 949-1393
						February 28, 2006
Mark Fusco
President and Chief Executive Officer
Aspen Technology, Inc.
Ten Canal Park
Cambridge, MA 02141

Re:	Aspen Technology, Inc.
	Form 10-K for Fiscal Year Ended June 30, 2005
	Forms 10-Q for Fiscal Quarter Ended September 30, 2005 and
	December 31, 2005

Dear Mr. Fusco:

      We have reviewed the above referenced filing and have the
following comments.  Please note that we have limited our review
to
the matters addressed in the comments below.  Where indicated, we
think you should revise your document in response to these
comments.
If you disagree, we will consider your explanation as to why our
comment is inapplicable or a revision is unnecessary.  Please be
as
detailed as necessary in your explanation.  In some of our
comments,
we may ask you to provide us with supplemental information so we
may
better understand your disclosure.  After reviewing this
information,
we may or may not raise additional comments.

	Please understand that the purpose of our review process is
to
assist you in your compliance with the applicable disclosure
requirements and to enhance the overall disclosure in your filing.
We look forward to working with you in these respects.  We welcome
any questions you may have about our comments or any other aspect
of
our review.  Feel free to call us at the telephone numbers listed
at
the end of this letter.

Form 10-K for the Year Ended June 30, 2005

Management Report on Internal Control over Financial Reporting,
page
M-1

1. We note for each of the identified material weaknesses noted in
Management`s Report on Internal Control over Financial Reporting
you
state, "As of a result of these identified weaknesses, material
post-
closing adjustments have been posted to the Company`s books and
records and its financial statements. These adjustments, which are
reflected in the accompanying financial statements for the year
ended, June 30, 2005, caused increases or decreases to accounts
receivable, cash, accrued expenses, revenue and general and
administrative expenses."  Are you referring to post-closing
adjustments that were made to the June 30, 2005 audited financial
statements?  If so, tell us how you determined none of these
adjustments related to prior periods and how you determined that
restatement of the financial statements in previously filed Forms
10-
Q was not required.

Note 1. Operations

(m) Intangible Assets, Goodwill and Impairment of Long Lived
Assets,
page F-15

2. We note your reference to an independent third party that was
used
to value the Company`s three reporting units.  Please note that
when
you refer to an independent valuation specialist you need to
disclose
the name of expert and include the expert`s consent with the
filing.
Refer to Section 436(b) of Regulation C.  Alternatively, you may
remove this reference.  Please tell us how you plan to comply with
this requirement.

Note 4. Acquisitions and Dispositions

(a) Dispositions During Fiscal Year 2005, page F-22

3. Tell us how the Company considered the guidance in paragraph 41
of
SFAS 144 in determining whether the sale of your AXSYS product
line
to Bentley Systems and your operator training business and
ownership
rights to the intellectual property to the Hyprotech engineering
products to Honeywell should be classified as discontinued
operations.  In this regard, we note your disclosures in Note 12
where you state, "The Company also evaluates certain subsets of
business segments by vertical industries as well as by product
categories."

Note 7. Preferred Stock

Series D Redeemable Convertible Preferred Stock, page F-25

4. Tell us how you evaluated the conversion feature associated
with
the Series D Stock to determine whether it was an embedded
derivative
that met the criteria for bifurcation under SFAS 133.  In this
regard, tell us how you considered the criteria in paragraph 12(a)
- -
12(c) of SFAS 133 and specifically tell us how you applied the
guidance in paragraph 61(l) in your analysis. Also, tell us how
you
considered the scope exception of paragraph 11(a) of SFAS 133 in
your
analysis. Specifically, we note in your disclosure that the Series
D
Redeemable Convertible Preferred Stock (Series D Stock) includes
anti-dilution rights that will adjust the conversion ratio
downwards
in the event that certain additional securities are issued at a
price
per share less than the current conversion price in effect. Tell
us
how you considered these provisions in determining whether the
embedded derivative qualified as a conventional convertible
instrument and met the scope exception of paragraph 4 of EITF 00-
19.
Include in your response, your consideration of EITF 05-2.   Also
include your analysis under paragraphs 12-32 of EITF 00-19, as
necessary.  In this regard, we note from your disclosures on page
25
that the Series D preferred stock contains registration rights
provisions.  Do they also contain liquidated damages provisions?
Tell us how you considered these provisions in your analysis. If
the
scope exception of paragraph 11(a) is not met, tell us whether you
have considered the conversion feature to be an embedded
derivative
that is subject to classification and measurement at fair value.
Also, please be advised that a beneficial conversion feature is
not
applicable when the conversion feature is bifurcated.

5. We note that in connection with the Series D Stock, you also
issued warrants.  Tell us how you analyzed the warrants pursuant
to
SFAS 133 and EITF 00-19.  In this regard, tell us whether the
Company
determined that the warrants met the scope exception of paragraph
11(a) of SFAS 133.  Provide us with your analysis using the
conditions outlined in paragraphs 12 to 32 of EITF 00-19 to
determine
whether the warrants should be classified in equity or as a
liability.  Specifically, we note from your disclosures on page 25
that the warrants have registration rights.  Do they also contain
liquidated damages provisions? Tell us how you considered these
provisions in your analysis.   If the scope exception of paragraph
11(a) has not been met, tell us why you have not classified the
warrants as a liability, initially measured at fair value, with
changes in fair value reported in earnings and disclosed in the
financial statements.

Form 10-Q For the Quarterly Period Ended September 30, 2005

Note 4. Stock-Based Compensation, page 8

6. We note that you adopted SFAS 123(R) in interim period ended
September 30, 2005.  Please tell us your consideration for the
disclosure requirements of SAB No. 107, Section H, Question 1
which
includes all disclosures required by paragraphs A240-242 of
Statement
123R.  If you determine that you have not provided the required
disclosures of this bulletin, tell us how you intend to comply
with
this bulletin.

7. We note that the Company`s valuation included volatility
assumptions of 85% and 42% for the stock option plans and purchase
plans, respectively.  You indicate that the expected volatility is
based on the historical volatility of the Company`s common stock
over
the period commensurate with or longer than the expected life of
the
options.  Please explain the significant decrease in the
volatility
assumption for the employee stock purchase plan from 100% for both
the fiscal year 2005 and the quarter ended September 30, 2004 to
42%
for the three months ended September 30, 2005 and December 31,
2005.
Similarly, please explain the change in the volatility estimates
for
the stock option plans from 100% for fiscal 2005 to 85% for the
three
months ended September 30, 2005 and December 31, 2005.

Forms 8-K filed September 13, 2005, November 8, 2005 and February
2,
2006

8. We note your use of non-GAAP measures under Item 9.01 of the
Form
8-Ks noted above which excludes a number of recurring items.  Tell
us
how you considered Question 8 of Frequently Asked Questions
Regarding
the Use of Non-GAAP Financial Measures to include the following
disclosures:

* the manner in which management uses the non-GAAP measure to
conduct
or evaluate its business;
* the economic substance behind management`s decision to use such
a
measure;
* the material limitations associated with use of the non-GAAP
financial measure as compared to the use of the most directly
comparable GAAP financial measure;
* the manner in which management compensates for these limitations
when using the non-GAAP financial measure; and
* the substantive reasons why management believes the non-GAAP
financial measure provides useful information to investors.

In this regard, we believe you should further enhance your
disclosures to comply with Item 10(e)(1)(i)(C) and (D) of
Regulation
S-K and Question 8 of the related FAQ to demonstrate the
usefulness
of your non-GAAP financial measures which excludes a number of
recurring items, especially since these measures appear to be used
to
evaluate performance.  Your current disclosures regarding the
reasons
for presenting these non-GAAP measures appear overly broad
considering that companies and investors may differ as to which
items
warrant adjustment and what constitutes operating performance.
Additionally, it is unclear why certain excluded items should not
be
considered in assessing your performance as several appear to be
recurring and integral to your performance.  For example, it is
unclear to us why amortization of intangible assets is not
relevant
for investors considering that the use of these assets contributes
to
generating revenue.  Similarly, it is unclear why excluding stock-
based compensation is appropriate considering that offering your
employees equity instruments appears to be a key incentive offered
in
the achievement of your goals as an organization.

9. We note your use of the term "pro forma information" in your
Form
8-Ks.  Please note that it is not appropriate for you to use this
term in your Form 8-Ks since you have not used that term as
contemplated in Regulation S-X.  It appears such disclosures
should
be referred to as non-GAAP measures.  Refer to footnote 12 to the
Final Rules for the Conditions for Use of Non-GAAP Financial
Measures.

 * * * * * * *

	As appropriate, please amend your filing and respond to these
comments within 10 business days or tell us when you will provide
us
with a response.  Please submit all correspondence and
supplemental
materials on EDGAR as required by Rule 101 of Regulation S-T.  You
may wish to provide us with marked copies of any amendment to
expedite our review.  Please furnish a cover letter with any
amendment that keys your responses to our comments and provides
any
requested information.  Detailed cover letters greatly facilitate
our
review.  Please understand that we may have additional comments
after
reviewing any amendment and your responses to our comments.

	 We urge all persons who are responsible for the accuracy and
adequacy of the disclosure in the filing reviewed by the staff to
be
certain that they have provided all information investors require
for
an informed decision.  Since the company and its management are in
possession of all facts relating to a company`s disclosure, they
are
responsible for the accuracy and adequacy of the disclosures they
have made.

	In connection with responding to our comments, please
provide,
in writing, a statement from the company acknowledging that:

* the company is responsible for the adequacy and accuracy of the
disclosure in the filing;

* staff comments or changes to disclosure in response to staff
comments do not foreclose the Commission from taking any action
with
respect to the filing; and

* the company may not assert staff comments as a defense in any
proceeding initiated by the Commission or any person under the
federal securities laws of the United States.

      In addition, please be advised that the Division of
Enforcement
has access to all information you provide to the staff of the
Division of Corporation Finance in our review of your filing or in
response to our comments on your filing.

      You may contact Patrick Gilmore at (202)-551-3406 or the
undersigned at (202) 551-3499 if you have any questions regarding
comments on the financial statements and related matters.

Sincerely,


      Kathleen Collins
      Accounting Branch Chief
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Mr. Mark Fusco
Aspen Technology, Inc.
February 28, 2006
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