<PAGE> 1
Filed Pursuant To Rule 424(b)(3)
Registration No. 333-63439
Prospectus Supplement No. 1
To Prospectus Dated December 10, 1998
$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. This Prospectus Supplement is not
complete without the Prospectus, and we have not authorized anyone to deliver or
use this Prospectus Supplement without the Prospectus.
In this Prospectus Supplement, we use some 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 January 21, 1999.
We are providing this Prospectus Supplement to add 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)
---------- ----------- ---------- --------- ---------- ---------- ------ ----------
<S> <C> <C> <C> <C> <C> <C> <C> <C>
Goldman, Sachs & Co. $1,539,000 1.8% $1,539,000 29,054 * 29,054 -- --
Reserve Convertible 650,000 * 650,000 12,271 * 12,271 -- --
Securities Fund
McMahan Securities 48,000 * 48,000 906 * 906 -- --
Company, L.P.
</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 January 21, 1999.
(2) Each Selling Securityholder has indicated that it intends to 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 24,926,493 shares of common stock outstanding on
January 21, 1999.
The date of this Prospectus Supplement is January 25, 1999.
