<PAGE> 1
Prospectus Supplement No. 6 Filed Pursuant to Rule 424(b)(3)
To Prospectus Dated December 10, 1998 Registration No. 333-63439
$86,250,000
Aspen Technology, Inc.
5 1/4% Convertible Subordinated Debentures due June 15, 2005
This Prospectus Supplement supplements the information we provided in
our December 10, 1998 Prospectus relating to our 5 1/4% Convertible
Subordinated Debentures due June 15, 2005 and the shares of our common stock
that we must issue upon conversion of those Debentures, and in our Prospectus
Supplements No. 1, No. 2, No. 3, No. 4 and No. 5. This Prospectus Supplement is
not complete without the supplemented Prospectus, and we have not authorized
anyone to deliver or use this Prospectus Supplement without the supplemented
Prospectus.
In this Prospectus Supplement, we use capitalized terms that we defined
in the Prospectus. You should read the Prospectus to understand those terms.
Unless we indicate otherwise, the information in this Prospectus Supplement is
as of June 25, 1999.
We are providing this Prospectus Supplement to update the following
information to the table in the Prospectus under the caption "Selling
Securityholders":
<TABLE>
<CAPTION>
Principal Amount of Shares of Common Shares of Common
Debentures Beneficially Stock Beneficially Stock Beneficially
Owned Prior to the Owned Prior to the Shares of Owned After the
Offering Amount of Offering Common Offering
---------------------- Debentures --------------------- Stock -------------------
Selling Securityholder Number Percent(1) Offered(2) Number(3) Percent(4) Offered(3) Number Percent(4)
- ------------------------------ ---------- ---------- ----------- --------- ---------- ----------- ------ ----------
<SC> <C> <C> <C> <C> <C> <C> <C> <C>
Deutsche Bank Securities...... $8,200,000 9.5% $8,200,000 154,808 * 154,808 -- --
31 West 52nd Street, 4th Floor
New York, NY 10019
</TABLE>
- --------------
* Less than one percent.
(1) For purposes of this Prospectus Supplement only, we have calculated this
percentage on the basis of $86,250,000 aggregate principal amount of
Debentures outstanding on June 25, 1999.
(2) This Selling Securityholder has indicated that it may offer all of the
Debentures that it owns. As a result, no Debentures will be owned after
the Offering.
(3) For purposes of this Prospectus Supplement only, we have calculated this
number using the conversion rate described on the front cover page of the
Prospectus.
(4) For purposes of this Prospectus Supplement only, we have calculated this
percentage on the basis of 24,950,159 shares of common stock outstanding
on June 25, 1999.
The date of this Prospectus Supplement is June 28, 1999.
