ASPEN TECHNOLOGY INC /MA/
S-3, 1997-11-04
COMPUTER PROGRAMMING SERVICES
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<PAGE>   1

    AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON NOVEMBER 4, 1997
                                                    Registration No. 333-
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                 -------------
                                    FORM S-3
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933
                                 -------------

                             ASPEN TECHNOLOGY, INC.
             (Exact name of registrant as specified in its charter)

             MASSACHUSETTS                             04-2739697
     (State or other jurisdiction                   (I.R.S. employer
   of incorporation or organization)             identification number)

                                 TEN CANAL PARK
                         CAMBRIDGE, MASSACHUSETTS 02141
                                 (617) 577-0100
    (Address, including zip code, and telephone number, including area code,
                  of registrant's principal executive offices)
                                 -------------
                              LAWRENCE B. EVANS
              Chairman of the Board and Chief Executive Officer
                            ASPEN TECHNOLOGY, INC.
                                Ten Canal Park
                        Cambridge, Massachusetts 02141
                                (617) 577-0100
   (Name, address, including zip code, and telephone number, including area
                         code, of agent for service)
                                 -------------
                                   Copies to:
          STEPHEN J. DOYLE, ESQ.                   MARK L. JOHNSON, ESQ.
    Vice President and General Counsel            FOLEY, HOAG & ELIOT LLP
          ASPEN TECHNOLOGY, INC.                  One Post Office Square
              Ten Canal Park                    Boston, Massachusetts 02109
      Cambridge, Massachusetts 02141
                                 -------------

     Approximate date of commencement of proposed sale to the public: As soon as
practicable after this Registration Statement becomes effective.
     If the only securities being registered on this Form are being offered
pursuant to dividend or interest reinvestment plans, please check the
following box.  / /
     If any of the securities being registered on this Form are to be offered
on a delayed or continuous basis pursuant to Rule 415 under the Securities
Act of 1933, other than securities offered only in connection with dividend
or interest reinvestment plans, check the following box.  /X/                
     If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following
box and list the Securities Act registration statement number of the earlier
effective registration statement for the same offering.  / / _______________
     If this Form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering.  / / __________
     If delivery of the prospectus is expected to be made pursuant to Rule
434, please check the following box.  / /

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
===============================================================================================================================
                                                              PROPOSED              PROPOSED
                                         AMOUNT                MAXIMUM               MAXIMUM
   TITLE OF EACH CLASS OF                 TO BE            OFFERING PRICE           AGGREGATE                AMOUNT OF
 SECURITIES TO BE REGISTERED           REGISTERED           PER SHARE(1)         OFFERING PRICE(1)        REGISTRATION FEE
- -------------------------------------------------------------------------------------------------------------------------------
<C>                                   <C>                     <C>                   <C>                       <C>
Common Stock, $.10 par value          283,350 shares          $33.19                $9,404,387                $2,850
===============================================================================================================================
</TABLE>
(1)   Estimated solely for the purpose of determining the registration fee. In
      accordance with Rule 457(c) under the Securities Act of 1933, the above
      calculation is based on the average of the high and low sale prices
      reported in the consolidated reporting system of the Nasdaq National
      Market on October 27, 1997.
                                 -------------

      THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL
FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(a)
THE SECURITIES ACT OF 1933 OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(a),
MAY DETERMINE.

================================================================================
<PAGE>   2
Information contained herein is subject to completion or amendment. A
registration statement relating to these securities has been filed with the
Securities and Exchange Commission. These securities may not be sold nor may
offers to buy be accepted prior to the time the registration statement becomes
effective. This prospectus shall not constitute an offer to sell or the
solicitation of an offer to buy nor shall there be any sale of these securities
in any State in which such offer, solicitation or sale would be unlawful prior
to registration or qualification under the securities laws of any such State.
<PAGE>   3
                  SUBJECT TO COMPLETION, DATED NOVEMBER 4, 1997

                                 283,350 SHARES

                             ASPEN TECHNOLOGY, INC.

                                  COMMON STOCK


      All of the 283,350 shares of Common Stock offered hereby are being sold by
the Selling Stockholders. See "Selling Stockholders." The Company will not
receive any of the proceeds from the sale of shares by the Selling Stockholders.

      The Company's Common Stock trades on the Nasdaq National Market under the
symbol "AZPN." On November 3, 1997, the closing sale price of the Common Stock,
as reported by the Nasdaq National Market, was $ 37.75 per share.

      The shares of Common Stock offered hereby may be sold from time to time by
the Selling Stockholders, or by pledgees, donees, transferees or other
successors in interest of the Selling Stockholders. Such sales may be made on
the Nasdaq National Market, or otherwise, at prices and on terms then prevailing
or at prices related to the then-current market prices, or in negotiated
transactions at negotiated prices. The shares may be sold by one or a
combination of the following: (a) a block trade in which the broker or dealer so
engaged will attempt to sell the shares as agent, but may position and resell a
portion of the block as principal to facilitate the transaction; (b) purchases
by a broker or dealer as principal and resale by such broker or dealer for its
account pursuant to this Prospectus; and (c) ordinary brokerage transactions and
transactions in which the broker solicits purchasers. Brokers or dealers will
receive commissions or discounts from Selling Stockholders in amounts to be
negotiated immediately prior to the sale. The Selling Stockholders will be
responsible for any discounts, concessions, commissions or other compensation
due to any broker or dealer in connection with the sale of any of the shares
offered hereby. All of the other expenses of this offering, estimated at $5,500,
will be paid by the Company. See "Plan of Distribution."


                                 -------------


      SEE "RISK FACTORS" COMMENCING ON PAGE 5 FOR A DISCUSSION OF CERTAIN
FACTORS THAT SHOULD BE CONSIDERED BY PROSPECTIVE PURCHASERS OF SHARES OF COMMON
STOCK OFFERED HEREBY.


                                 -------------


    THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES
     AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE
      SECURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION
          PASSED UPON THE ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY
              REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.



                                          , 1997
<PAGE>   4
                              AVAILABLE INFORMATION

      The Company is subject to the informational requirements of the Securities
Exchange Act of 1934, as amended (the "Exchange Act"), and in accordance
therewith files reports and other information with the Securities and Exchange
Commission (the "Commission"). Such reports and other information may be
inspected and copies may be obtained (at prescribed rates) at the Commission's
Public Reference Section, 450 Fifth Street, N.W., Room 1024, Washington D.C.
20549, and at the Commission's Regional Offices at Northwestern Atrium Center,
500 West Madison Street, Suite 1400, Chicago, Illinois 60661-2511 and 7 World
Trade Center, Suite 1300, New York, New York 10048. Reports and other
information concerning the Company also may be inspected at the offices of the
Nasdaq Stock Market, 1735 K Street, N.W., Washington D.C. 20006-1500.

      This Prospectus constitutes part of a Registration Statement on Form S-3
(the "Registration Statement") filed by the Company with the Commission under
the Securities Act of 1933, as amended (the "Securities Act"). This Prospectus
does not contain all of the information contained in the Registration Statement,
and reference is hereby made to the Registration Statement and related exhibits
for further information with respect to the Company and the securities offered
hereby. Any statements contained herein concerning the provisions of any
document are not necessarily complete, and, in such instance, reference is made
to the copy of such document filed as an exhibit to the Registration Statement
or otherwise filed with the Commission. Each such statement is qualified in its
entirety by such reference.


                      INFORMATION INCORPORATED BY REFERENCE

      The following documents heretofore filed by the Company with the
Commission pursuant to the Exchange Act are incorporated herein by reference:

      (1)   the Company's Annual Report on Form 10-K for the fiscal year ended
            June 30, 1997 (the "Annual Report");

      (2)   the Company's Current Report on Form 8-K dated October 9, 1997; and

      (3)   the Company's preliminary Proxy Statement dated October 29, 1997 to
            be used in connection with its Annual Meeting of Stockholders to be
            held on December 16, 1997.

      All reports and other documents subsequently filed by the Company pursuant
to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of this
Prospectus and prior to the termination of the offering made hereby shall be
deemed to be incorporated by reference herein and to be a part hereof from the
date of the filing of such reports and documents. Any statement contained in a
document incorporated or deemed to be incorporated by reference herein shall be
deemed to be modified or superseded for purposes of this Prospectus to the
extent that a statement contained herein modifies or supersedes such statement.
Any statement so modified or superseded shall not be deemed, except as so
modified or superseded, to constitute a part of the Registration Statement or
this Prospectus.

      Any person to whom a copy of this Prospectus is delivered may obtain,
without charge, upon written or oral request, a copy of any of the documents
incorporated by reference herein, except for the exhibits to such documents
(other than exhibits expressly incorporated by reference into such documents).
Requests for such documents should be addressed to the Manager of Investor
Relations of the Company, Ten Canal Park, Cambridge, Massachusetts 02141 or
directed to the Manager of Investor Relations at either telephone number (617)
577-0100 or e-mail address [email protected].


                                       2
<PAGE>   5
- -------------------------------------------------------------------------------
                              PROSPECTUS SUMMARY

      The following summary is qualified in its entirety by the more detailed
information and financial statements, including the notes thereto, appearing
elsewhere in this Prospectus or incorporated by reference herein.

                                   THE COMPANY

      Aspen Technology, Inc. (the "Company" or "AspenTech") is a leading
supplier of off-the-shelf software products and services for the analysis,
design and automation of manufacturing facilities by companies in the process
industries, including the chemicals, petrochemicals, petroleum, pharmaceuticals,
pulp and paper, electric power, and food and consumer products industries.
Process manufacturers use AspenTech's solutions, a family of software products
and services, to design, operate and manage manufacturing processes more
efficiently, safely and profitably.

      AspenTech provides a sophisticated, integrated family of off-the-shelf
software products for use across the entire process manufacturing life-cycle,
from "off-line" applications used primarily in research and development and
engineering to "on-line" applications used primarily in production. The
Company's off-line software is used by engineers on desktop computers primarily
to simulate and predict the performance of manufacturing processes in connection
with the design of new facilities or processes and the analysis of existing
facilities or processes. AspenTech's on-line software, which is connected
directly to plant instrumentation, enables the real-time adjustment of
production variables in response to constantly changing operating conditions to
improve process efficiency, planning and scheduling. AspenTech's product
offerings are classified in four categories: modeling; planning and scheduling;
information management systems ("IMS"); and advanced process control ("APC") and
optimization. Chemical engineers who work in the off-line research and
development and engineering stages of plant and process design and analysis are
the principal users of modeling products, while chemical and control engineers
who work in the on-line stages of real-time plant operation are the primary
users of IMS, APC and optimization software and services.

      The Company's modeling software mathematically simulates and predicts the
performance of manufacturing processes under varying equipment configurations
and operating conditions, enabling chemical engineers to design cost-effective,
efficient processes that comply with environmental and safety requirements.
AspenTech's planning and scheduling software is used by petroleum refiners and
chemical manufacturers for feedstock selection, product mix optimization,
logistics, scheduling, process unit optimization, and investment planning.
AspenTech's IMS software is used by process manufacturers to gather and analyze
large volumes of real-time plant operations data in order to better understand
actual performance within a complex process manufacturing facility. IMS software
allows customers to compare actual performance with theoretical benchmarks
derived from models and to make appropriate adjustments on a real-time basis.
AspenTech's APC and optimization software products are designed to enable
customers to achieve superior operating performance by continuously adjusting
key process variables to maintain optimal target levels under constantly
changing conditions.

      The Company initially became a provider of IMS software and services
through its acquisition of Industrial Systems, Inc. ("ISI") in May 1995, and
expanded its IMS capabilities through its acquisition of Setpoint, Inc.
("Setpoint") in February 1996. AspenTech significantly enhanced its APC and
optimization software offerings through the Setpoint acquisition as well as its
acquisition of Dynamic Matrix Control Corporation ("DMCC") in January 1996.
AspenTech further extended its family of on-line solutions to include economic
planning and scheduling capabilities by acquiring the assets of Bechtel
Corporation's PIMS (Process Industries Modeling System) business in December
1996. In separate transactions in September 1997, AspenTech acquired NeuralWare,
Inc. ("NeuralWare"), a provider of neural network and related technologies that
AspenTech intends to incorporate into its APC, process modeling and IMS
software, and Special Analysis and Simulation Technology Limited ("SAST"), a
provider of dynamic simulation and operator training services and applications.

- -------------------------------------------------------------------------------

                                       3
<PAGE>   6
- -------------------------------------------------------------------------------

      AspenTech combines its integrated family of off-the-shelf software
products with design and implementation consulting services in order to market a
complete solution to its customers. The Company significantly strengthened its
on-line consulting services through its acquisitions of DMCC and Setpoint in
early 1996, and expanded the global reach of its consulting services
organization with the acquisition in October 1996 of the process control
division of Cambridge Control Limited ("Cambridge Control"). AspenTech believes
its ability to offer a complete solution of both industry-leading software and
sophisticated process engineering expertise is an important source of
competitive differentiation.

      The Company was founded in 1981 and is a Massachusetts corporation. At the
1997 Annual Meeting of Stockholders to be held in December 1997, the Company's
stockholders will consider, among other things, a proposal to reincorporate
AspenTech in Delaware. AspenTech's executive offices are located at Ten Canal
Park, Cambridge, Massachusetts 02141, and its telephone number is (617)
949-1000.


                                  THE OFFERING

      All of the 283,350 shares of Common Stock offered hereby are being sold by
the Selling Stockholders. The offered shares were issued to the Selling
Stockholders pursuant to (i) the Agreement and Plan of Reorganization dated as
of August 1, 1997 between the Company, the Company's wholly owned subsidiary AT
Acquisition Corp., NeuralWare and the former stockholders of NeuralWare, under
which a portion of the offered shares were issued in exchange for the
outstanding capital stock of NeuralWare, and (ii) the Share Exchange Agreement
dated as of August 28, 1997 between the Company, SAST, The SAST Corporation
Limited, S.A.S.T. Process Limited, Special Analysis and Computing Services
Limited, SAST, Inc. and the founders of The SAST Corporation Limited, under
which the remainder of the offered shares were issued for all of the outstanding
capital stock of The SAST Corporation Limited.

      Under the agreement with respect to the acquisition of the capital stock
of NeuralWare, Inc., the Company is obligated to keep the Registration Statement
in effect until all of the shares issued in exchange for such capital stock and
offered hereby (a) have been sold or (b) a period of ninety days has elapsed
since the date of this Prospectus. Under the agreement with respect to the
acquisition of the capital stock of The SAST Corporation Limited, the Company is
obligated to keep the Registration Statement in effect until all of the shares
issued in exchange for such capital stock and offered hereby (a) have been sold,
(b) can be distributed to the public pursuant to Rule 144 under the Securities
Act, or (c) have been otherwise transferred to third parties in transactions
resulting in the shares being freely tradeable.

      The Company will not receive any of the proceeds from the sale of shares
by the Selling Stockholders. See "Use of Proceeds."


                                 -------------


                   "AspenTech" is a trademark of the Company.

- -------------------------------------------------------------------------------

                                       4
<PAGE>   7
                                  RISK FACTORS

      THIS PROSPECTUS CONTAINS AND INCORPORATES BY REFERENCE FORWARD-LOOKING
STATEMENTS WITHIN THE MEANING OF SECTION 27A OF THE SECURITIES ACT OF 1933 AND
SECTION 21E OF THE SECURITIES EXCHANGE ACT OF 1934. THE COMPANY'S ACTUAL RESULTS
COULD DIFFER MATERIALLY FROM THE RESULTS CONTEMPLATED IN THE FORWARD-LOOKING
STATEMENTS AS A RESULT OF A NUMBER OF FACTORS, INCLUDING THE RISK FACTORS SET
FORTH BELOW.

      Dependence Upon Increased Market Penetration. Increased use in the process
industries, particularly the chemicals and petroleum industries, of software and
services for the analysis, design and automation of process manufacturing plants
in general and of the Company's software products and services in particular is
critical to the Company's future growth. The Company believes that a number of
factors will determine its ability to achieve increased market penetration.
These factors include product performance, accuracy of results, ease of
implementation and use, breadth and integration of product offerings,
reliability and scope of applications. Failure of the Company to achieve
increased market penetration in the process industries would substantially
restrict the future growth of the Company and could have a material adverse
effect on the Company's business, operating results and financial condition. See
"Item 1. Business--The AspenTech Advantage" and "--Strategy" in the Annual
Report.

      Fluctuations in Quarterly Operating Results. The Company's operating
results have fluctuated in the past and may fluctuate significantly in the
future as a result of a variety of factors, including purchasing patterns,
timing of new products and enhancements by the Company and its competitors, and
fluctuating foreign economic conditions. In addition, the Company ships software
products within a short period after receipt of an order and typically does not
have a material backlog of unfilled orders of software products. Therefore,
revenues from software licenses in any quarter are substantially dependent on
orders booked in that quarter. Historically, a majority of each quarter's
revenues from software licenses has come from license contracts that have been
effected in the final weeks of that quarter. The revenues for a quarter
typically include a number of large orders. If the timing of any of these orders
is delayed, it could result in a substantial reduction in revenues for that
quarter. Since the Company's expense levels are based in part on its
expectations as to future revenues, the Company may be unable to adjust spending
in a timely manner to compensate for any revenue shortfall and any revenue
shortfalls would likely have a disproportionate adverse effect on net income.
Prior to fiscal 1996, the Company experienced a net loss for the first quarter
of each fiscal year, in part because a substantial portion of the Company's
revenues is derived from countries other than the United States where business
is slow during the summer months and also in part because of the timing of
renewals of software licenses. The Company expects that these factors will
continue to affect its operating results and that the Company may experience net
losses in the initial quarter of future fiscal years. See "Item 7. Management's
Discussion and Analysis of Financial Condition and Results of
Operations--Quarterly Results" in the Annual Report.

      Concentration of Revenues in the Chemicals and Petroleum Industries. The
Company derives a significant portion of its revenues from companies in the
chemicals and petroleum industries. Accordingly, the Company's future success is
dependent upon the continued demand for modeling software by companies in the
chemicals industry, and for planning and scheduling, IMS, APC and optimization
software and services by companies in the chemical and petroleum industries. The
chemical and petroleum industries are highly cyclical. The Company believes that
economic downturns in the United States, Europe, Japan, Asia and South America
and pricing pressures experienced by chemical and petroleum companies in
connection with cost-containment measures have led to delays and reductions in
certain capital and operating expenditures by many of such companies worldwide.
The Company's revenues have in the past been, and may in the future be, subject
to substantial period-to-period fluctuations as a consequence of such industry
patterns, as well as general domestic and foreign economic conditions and other
factors affecting spending by companies in the Company's target process
industries. There can be no assurance that such factors will not have a material
adverse effect on the


                                       5
<PAGE>   8
Company's business, operating results and financial condition. See "Item 7.
Management's Discussion and Analysis of Financial Condition and Results of
Operations--Results of Operations" in the Annual Report.

      Product Development and Technological Change. The market for software and
services for the analysis, design and automation of process manufacturing plants
is characterized by continual change and improvement in computer hardware and
software technology. The Company's future success will depend on its ability to
enhance its current software products and services, to introduce new software
products and services that keep pace with technological developments, and to
continue to address the changing needs of its customers. There can be no
assurance that the Company will be successful in developing and marketing new
and enhanced products and services, or that its products and services will
continue to address adequately the needs of the marketplace. Like many other
software products, the Company's products have on occasion contained undetected
errors or "bugs." In addition, because new releases of the Company's products
are initially installed only by a small number of customers, any errors or
"bugs" in those new releases may not be detected for a number of months after
the delivery of the software. If the Company's products do not perform
substantially as expected or are not accepted in the marketplace, the Company's
business, operating results and financial condition would be materially
adversely affected. See "Item 1. Business--Product Development" in the Annual
Report.

      Dependence on Key Personnel. The Company's future success depends to a
significant extent on Lawrence B. Evans, the Company's chief executive officer,
its other executive officers, and certain key technical, managerial and
marketing personnel. The loss of the services of any of these individuals or
groups of individuals could have a material adverse effect on the Company's
business, operating results and financial condition. None of the Company's
executive officers has entered into an employment agreement with the Company,
and the Company does not have, and is not contemplating securing, any
significant amount of key-man life insurance on any of its executive officers or
other key employees. The Company believes that its future success also will
depend significantly upon its ability to attract, motivate and retain additional
highly skilled technical, managerial and marketing personnel. Competition for
such personnel is intense, and there can be no assurance that the Company will
be successful in attracting and retaining the personnel it requires to continue
to grow and operate profitably. See "Item 1. Business--Employees" in the Annual
Report.

      Product Liability. The sale and implementation of on-line applications by
the Company may entail the risk of product liability claims. The Company's APC
and optimization software products and services are used in the design,
operation and management of manufacturing processes at large facilities, and any
failure by the software at those facilities could result in significant claims
for damages or for violations of environmental, safety and other laws and
regulations. The Company's agreements with its customers generally contain
provisions designed to limit the Company's exposure to potential product
liability claims. It is possible, however, that the limitation of liability
provisions contained in the Company's license agreements may not be effective as
a result of federal, state or local laws or ordinances or unfavorable judicial
decisions. A successful product liability claim against the Company could have a
material adverse effect upon the Company's business, operating results and
financial condition.

      Migration to Microsoft Windows; Emergence of Other Standards. AspenTech
believes that operating systems such as Microsoft Windows, due to their
interoperability and customization capabilities, are increasingly the preferred
choice of certain of its customers. AspenTech has developed Windows 95 versions
of its software products and Windows NT versions of most of its core products.
It has developed a Windows NT version of ASPEN PLUS which is in test stages and
is developing a Windows NT version of RT-OPT. There can be no assurance of
customer acceptance of Windows versions of all products, or that they will be
competitive with offerings from the Company's competition. Although the Company
does not believe that there are currently other operating platforms which are in
demand by customers, there can be no assurance that customers will not migrate
to or require compatibility with other systems such as Java. The Company is also
aware of customer concerns that its products be able to handle the date change
on and after the year 2000 and has established a


                                       6
<PAGE>   9
compliance program to test and, if necessary, modify new versions of its
products. Any such failure or delay in developing and releasing new operating
systems versions or testing or modifying its software to be year 2000 compliant
could affect the Company's competitive position or lead to product obsolescence
in the future. See "Item 1. Business--Product Development" and "Competition" in
the Annual Report.

      Dependence on Proprietary Technology. The Company regards its software as
proprietary and relies on a combination of copyright, patent, trademark and
trade secret laws, license and confidentiality agreements, and software security
measures to protect its proprietary rights. AspenTech has United States patents
for the expert guidance system in its proprietary graphical user interface,
simulation and optimization methods in its optimization software, a process flow
diagram generator in its planning and scheduling software, and a process
simulation apparatus in its polymers software. The Company has registered or
applied to register certain of its significant trademarks in the United States
and in certain other countries. The Company generally enters into non-disclosure
agreements with its employees and customers, and historically has restricted
access to its software products' source codes, which it regards as proprietary
information. In a few cases, the Company has provided copies of the source code
for certain products to customers solely for the purpose of special
customization of the products and has deposited copies of the source code for
certain products in third-party escrow accounts as security for on-going service
and license obligations. In these cases, the Company relies on nondisclosure and
other contractual provisions to protect its proprietary rights.

      The laws of certain countries in which the Company's products are
distributed do not protect the Company's products and intellectual property
rights to the same extent as the laws of the United States. The laws of many
countries in which the Company licenses its products protect trademarks solely
on the basis of registration. The Company currently possesses a limited number
of trademark registrations in certain foreign jurisdictions and does not possess
any foreign copyright or patent registrations. The Company derived more than 50%
of its revenues from customers outside the United States in fiscal 1995 and 1997
and approximately 45% of its revenues from customers outside the United States
in fiscal 1996.

      There can be no assurance that the steps taken by the Company to protect
its proprietary rights will be adequate to deter misappropriation of its
technology or independent development by others of technologies that are
substantially equivalent or superior to the Company's technology. Any such
misappropriation of the Company's technology or development of competitive
technologies could have a material adverse effect on the business, results of
operations and financial condition of the Company. The Company could incur
substantial costs in protecting and enforcing its intellectual property rights.
Moreover, from time to time third parties may assert patent, trademark,
copyright and other intellectual property rights to technologies that are
important to the Company. In such an event, the Company may be required to incur
significant costs in litigating a resolution to the asserted claims. There can
be no assurance that such a resolution would not require that the Company pay
damages or obtain a license of a third party's proprietary rights in order to
continue licensing its products as currently offered or, if such a license is
required, that it will be available on terms acceptable to the Company. See
"Item 1. Business--Proprietary Rights."

      Competition. The Company's software products compete with software tools
that are internally developed by companies in the process industries and with
certain process modeling, planning and scheduling, IMS, APC and optimization
software products that are sold by a number of commercial suppliers. AspenTech's
primary commercial competitors in the process modeling software market are
Simulation Sciences Inc., Hyprotech, Ltd. (a subsidiary of AEA Technology plc)
and Chemstations, Inc. In the planning and scheduling market, the Company
competes with Bonner and Moore Associates, Inc., Haverly Systems, Inc.,
Chesapeake Decision Science, Inc., and Ernst & Young Wright Killen. In the IMS
market, AspenTech primarily competes with Oil Systems Inc. and Biles and
Associates (which entered into an agreement to be acquired by Simulation
Sciences, Inc. in August 1997) and, to a lesser extent, with distributed control
system vendors such as Honeywell Inc. In the APC and optimization markets,
AspenTech competes with the industrial automation and control business unit of
Honeywell Inc., which primarily sells distributed control system hardware, as
well as with Pavilion


                                       7
<PAGE>   10
Technologies, Inc. and the Simcon division of ABB Asea Brown Boveri (Holding)
Ltd. Several small competitors, including Treiber Control, focus exclusively on
the APC market. There has also been a number of acquisitions and consolidations
which expand the breadth of product and service offerings by certain of these
competitors including the acquisition of both Interplant Consulting, Inc., a
provider of real-time database applications, and Measurex Corporation, a
provider of control systems in the pulp and paper industry, by Honeywell, Inc.;
Hyprotech, Ltd. by AEA Technologies plc; and Visual Solutions, Inc., a provider
of simulation software and services, the on-line technology division of Raytheon
Engineers Contractors, Inc. and Biles and Associates, a provider of information
management and control solutions, by Simulation Sciences, Inc. Emergence of a
new competitor or the consolidation of existing competitors could adversely
affect the Company's business, operating results and financial condition.
Certain competitors also supply related hardware products to existing and
potential customers of AspenTech, and may have established relationships that
afford the competitors an advantage in supplying software and services to those
customers. The Company's continued success depends on its ability to compete
effectively with its commercial competitors and to persuade prospective
customers to use the Company's products and services instead of, or in addition
to, software developed internally or services provided by their own personnel.
In light of these factors, there is no assurance that the Company will be able
to maintain its competitive position. See "Item 1. Business--Competition" in the
Annual Report.

      Management of Growth. Since fiscal 1990, the Company has experienced
substantial growth in the number of its employees, the scope of its operating
and financial systems, and the geographic area of its operations. The Company's
operations have expanded significantly through both internally generated growth
and acquisitions, particularly the acquisitions of DMCC and Setpoint in the
third quarter of fiscal 1996. This growth has resulted in an increase in the
level of responsibility for management personnel. To manage its growth
effectively, the Company must continue to implement and improve its operating
and financial systems, and to retain and increase its employee base. There can
be no assurance that the management systems currently in place will be adequate
or that the Company will be able to manage the Company's recent or future growth
successfully, and any failure to do so could have a material adverse effect on
the Company's business, operating results and financial condition. See "Item 7.
Management's Discussion and Analysis of Financial Condition and Results of
Operations--Results of Operations" in the Annual Report.

      International Operations. The Company derived more than 50% of its
revenues from customers outside the United States in fiscal 1995 and 1997 and
approximately 45% of its revenues from customers outside the United States in
fiscal 1996. The Company anticipates that revenues from customers outside the
United States will continue to account for a significant portion of its total
revenues in the foreseeable future. The Company's operations outside the United
States are subject to certain risks, including unexpected changes in regulatory
requirements, exchange rates, tariffs and other barriers, political and economic
instability, difficulties in managing distributors or representatives,
difficulties in staffing and managing foreign subsidiary operations,
difficulties or delays in translating products and product documentation into
foreign languages, and potentially adverse tax consequences. There can be no
assurance that any of these factors will not have a material adverse effect on
the Company's business, operating results and financial condition.

      The impact of future exchange rate fluctuations on the Company's financial
condition and results of operations cannot be accurately predicted. In recent
years, the Company has increased the extent to which it denominates arrangements
with customers outside the United States in the currencies of the country in
which the software or services are provided. From time to time the Company has
engaged in, and may continue to engage in, hedges of a significant portion of
installment contracts denominated in foreign currencies. There can be no
assurance that any hedging policies implemented by the Company will be
successful or that the cost of such hedging techniques will not have a
significant impact on the Company's business, results of operations or financial
condition. See "Item 7. Management's Discussion and Analysis of Financial
Condition and Results of Operations" in the Annual Report.


                                       8
<PAGE>   11
      Risks Associated With Future Acquisitions. To expand its markets, the
Company's business strategy includes growth through additional acquisitions.
Identifying and pursuing acquisition opportunities and integrating acquired
products and businesses requires a significant amount of management time and
skill. There can be no assurance that the Company will be able to identify
suitable acquisition candidates, consummate any acquisition on acceptable terms
or successfully integrate any acquired business into the Company's operations.
There also can be no assurance that any future acquisition will not have an
adverse effect upon the Company's operating results, particularly in the fiscal
quarters immediately following consummation of the acquisition while the
acquired business is being integrated into the Company's operations. As a result
of acquisitions, the Company may encounter unexpected liabilities and
contingencies associated with the acquired businesses. The Company may use
Common Stock or Preferred Stock or may incur additional long-term indebtedness
or a combination thereof for all or a portion of the consideration to be paid in
future acquisitions. The issuance of Common Stock or Preferred Stock in
acquisitions could result in dilution to existing Stockholders, while the use of
cash reserves or significant debt financing to fund acquisitions could reduce
the Company's liquidity.

      Potential Volatility of Stock Price. The stock market has from time to
time experienced extreme price and volume fluctuations, particularly in the high
technology sector, and those fluctuations have often been unrelated to the
operating performance of particular companies. In addition, factors such as
announcements of technological innovations or new products by the Company or its
competitors, as well as market conditions in the computer software or hardware
industries, may have a significant impact on the market price of the Company's
Common Stock.

      Effect of Certain Charter and By-Law Provisions and Anti-Takeover
Provisions; Possible Issuances of Preferred Stock. The Company's Restated
Articles of Organization, its By-Laws and certain Massachusetts laws contain
provisions that may discourage acquisition bids for the Company and that may
reduce the temporary fluctuations in the trading price of the Company's Common
Stock which are caused by accumulations of stock, thereby depriving Stockholders
of certain opportunities to sell their stock at temporarily higher prices or
receive a premium for their shares as part of an acquisition of the Company.
Preferred Stock may be issued by the Company in the future without Stockholders
approval and upon such terms as the Board of Directors may determine. The rights
of the holders of Common Stock will be subject to, and may be adversely affected
by, the rights of the holders of any Preferred Stock that may be issued in the
future. The issuance of Preferred Stock, while providing desirable flexibility
in connection with possible acquisitions and other corporate purposes, could
have the effect of making it more difficult for a third party to acquire, or of
discouraging a third party from acquiring, a majority of the outstanding stock
of the Company. The Company has no present plans to issue any shares of
Preferred Stock. In addition, on October 9, 1997, the Board of Directors of the
Company declared a dividend of one Right for each outstanding share of Common
Stock. These Rights have certain anti-takeover effects and will cause
substantial dilution to a person or group that attempts to acquire the Company
without either conditioning an offer on substantially all of the Rights being
acquired or obtaining the prior approval of the Board of Directors of the
Company. For a more complete description of the Rights, see the Company's
Current Report on Form 8-K dated October 9, 1997, which is incorporated by
reference herein.


                                 USE OF PROCEEDS

      The Company will not receive any proceeds from the sale of Common Stock by
the Selling Stockholders, nor will any such proceeds be available for use by the
Company or otherwise for the Company's benefit. See "Selling Stockholders."


                              SELLING STOCKHOLDERS

      The following table sets forth certain information with respect to the
beneficial ownership of the Company's Common Stock by the Selling Stockholders
as of November 3, 1997 and as adjusted to reflect the sale of the shares of
Common Stock offered hereby. Except as indicated, each of the Selling
Stockholders possesses sole voting and investment power with respect to shares,
subject to community property laws where applicable.


                                       9
<PAGE>   12
<TABLE>
<CAPTION>
                                                                                                 SHARES TO BE
                                                           SHARES                             BENEFICIALLY OWNED
                                                     BENEFICIALLY OWNED                        AFTER OFFERING IF
                                                      PRIOR TO OFFERING        NUMBER OF        ALL SHARES SOLD
                                                    -------------------      SHARES BEING     ------------------ 
NAME                                                NUMBER      PERCENT        OFFERED        NUMBER     PERCENT
- ----                                                ------      -------      ------------     ------     -------

<S>                                                  <C>            <C>         <C>            <C>           <C>
Martyn E. Blanchard                                 72,082          *           64,874         7,208         *
Paul M. Davies and Catherine E. Davies, 
   Trustees under deed of trust
   dated 10/1/87                                     1,173          *            1,056           117         *
Johannes M. Eskes(1)                                72,083          *           64,875         7,208         *
J M Eskes Trust(1)                                  72,083          *           64,875         7,208         *
Graham W. Griffiths(2)                              72,083          *           64,875         7,208         *
G W Griffiths Trust(2)                              72,083          *           64,875         7,208         *
John P. Guiver                                         606          *              546            60         *
Highland Capital Investors                             689          *              620            69         *
Tijana Illich                                          162          *              146            16         *
Alan G. Kay                                         72,082          *           64,874         7,208         *
Eric A. King                                             1          *                1            --        --
Kenneth A. Kleinburg                                    20          *               18             2         *
Casimir Klimasauskas(3)                             16,688          *           15,018         1,670         *
Celestine M. Klimasauskas                              324          *              292            32         *
R. Jane Klimasauskas(4)                             16,688          *           15,018         1,670         *
Pierre E. and Sue Ellen Leroy                          827          *              744            83         *
Bryan Loofbourrow                                       64          *               58             6         *
John W. Loofbourrow(5)                               2,657          *            2,392           265         *
John W. Loofbourrow Associates, Inc. 
   Profit Sharing Plan(5)                            2,657          *            2,392           265         *
Tod H. Loofbourrow                                     250          *              225            25         *
Wayne R. Loofbourrow                                    32          *               29             3         *
Jeffrey L. Morby                                       920          *              828            92         *
Pasadena  Services, Inc. Defined Benefit    
   Pension Plan f/b/o Noel R. Hanson                    46          *               41             5         *
Garret A. Pelton                                       608          *              547            61         *
Donald H. Putnam and Susan W. Kellison(6)              898          *              808            90         *
Eileen M. Putnam                                        46          *               41             5         *
Erroll A. Rhodes                                        40          *               36             4         *
David Satchel                                           46          *               41             5         *
David G. Stork                                         406          *              365            41         *
</TABLE>
 ........................
*    Percentage of shares beneficially owned is less than 1.0%.

(1)  Shares beneficially owned prior to the offering consist of 16,320 shares
     held of record by Mr. Eskes (of which 14,688 shares are being offered
     hereby) and 55,762 shares held of record by J M Eskes Trust (of which
     50,187 shares are being offered hereby), of which Mr. Eskes is a trustee.

(2)  Shares beneficially owned prior to the offering consist of 16,320 shares
     held of record by Mr. Griffiths (of which 14,688 shares are being offered
     hereby) and 55,762 shares held of record by G W Griffiths Trust (of which
     50,187 shares are being offered hereby), of which Mr Griffiths is a
     trustee.

(3)  Includes 8,425 shares held of record by Mr. Klimasauskas's spouse, R. Jane
     Klimasauskas, of which 7,582 shares are being offered hereby.

(4)  Includes 8,263 shares held of record by Ms. Klimasauskas's spouse, Casimir
     Klimsauskas, of which 7,436 shares are being offered hereby.

(5)  Shares beneficially owned prior to offering consist of 1,544 shares held of
     record by Mr. Loofbourrow (of which 1,390 shares are being offered hereby)
     and 1,113 shares held of record by John W. Loofbourrow Associates, Inc.
     Profit Sharing Plan (of which 1,002 shares are being offered hereby).

(6)  Shares beneficially owned prior to offering consist of 810 shares held of
     record by Mr. Putnam (of which 729 shares are being offered hereby) and
     88 shares held of record by Mr. Putnam and Ms. Kellison jointly (of which
     79 shares are being offered hereby).
<PAGE>   13
                              PLAN OF DISTRIBUTION

      This Prospectus and the Registration Statement are in furtherance of a
"shelf" registration pursuant to Rule 415 promulgated by the Commission under
the Securities Act. Pursuant to registration rights arrangements entered into
with the Selling Stockholders, the Company is obligated to keep the "shelf"
registration effective until all of the shares offered have been sold, subject
to suspension by AspenTech in certain events.

      The shares offered hereby may be sold from time to time by the Selling
Stockholders, or by pledgees, donees, transferees or other successors in
interest of the Selling Stockholders. Such sales may be made on the Nasdaq
National Market, or otherwise, at prices and on terms then prevailing or at
prices related to the then-current market prices, or in negotiated transactions
at negotiated prices. The shares may be sold by one or a combination of the
following: (a) a block trade in which the broker or dealer so engaged will
attempt to sell the shares as agent, but may position and resell a portion of
the block as principal to facilitate the transaction; (b) purchases by a broker
or dealer as principal and resale by such broker or dealer for its account
pursuant to this Prospectus; and (c) ordinary brokerage transactions and
transactions in which the broker solicits purchasers. In effecting sales,
brokers or dealers engaged by the Selling Stockholders may arrange for other
brokers or dealers to participate. Brokers or dealers will receive commissions
or discounts from Selling Stockholders in amounts to be negotiated immediately
prior to the sale. The Selling Stockholders and any broker-dealers that
participate in the distribution may be deemed to be "underwriters" within the
meaning of Section 2(11) of the Securities Act, and any commission received by
them and any profit on the resale of shares sold by them may be deemed to be
underwriting discounts and commissions.

      Upon the Company being notified by the Selling Stockholders that any
material arrangement has been entered into with a broker-dealer for the sale of
shares through a block trade, special offering, exchange distribution or
secondary distribution or a purchase by a broker or dealer, a supplemented
prospectus will be filed, if required, pursuant to Rule 424(c) under the
Securities Act, setting forth (i) the name of each of the participating
broker-dealers, (ii) the number of shares involved, (iii) the price at which
such shares were sold, (iv) the commissions paid or discounts or concessions
allowed to such broker-dealers, where applicable, (v) a statement to the effect
that such broker-dealers did not conduct any investigation to verify the
information set out or incorporated by reference in this Prospectus and (vi)
other facts material to the transaction.


                                  LEGAL MATTERS

      The validity of the shares of Common Stock offered hereby has been passed
upon for the Company by Foley, Hoag & Eliot LLP, Boston, Massachusetts.


                                     EXPERTS

      The consolidated balance sheets of the Company and its subsidiaries as of
June 30, 1996 and 1997 and the related consolidated statements of operations,
stockholders' equity and cash flows for the years ended June 30, 1995, 1996 and
1997 incorporated by reference herein have been audited by Arthur Andersen LLP,
independent public accountants, as indicated in their report with respect
thereto, and are incorporated by reference herein in reliance upon the authority
of said firm as experts in giving said report.



                                       11
<PAGE>   14
================================================================================

      No broker, dealer or any other person has been authorized to give any
information or to make any representations in connection with this offering
other than those contained in this Prospectus, and, if given or made, such
information or representations must not be relied upon as having been
authorized by the Company or the Selling Stockholders. This Prospectus does not
constitute an offer to sell or a solicitation of an offer to buy any securities
other than the shares of Common Stock to which it relates or an offer to, or a
solicitation of, any person in any jurisdiction where such an offer or
solicitation would be unlawful. Neither the delivery of this Prospectus nor any
sale made hereunder shall, under any circumstances, create any implication that
there has been no change in the affairs of the Company since the date hereof or
that information contained herein is correct as of any time subsequent to its
date.


                                -----------------

                                TABLE OF CONTENTS

                                -----------------


                                                                            Page
                                                                            ----
Available Information................................................         2

Information Incorporated by Reference................................         2

Prospectus Summary...................................................         3

Risk Factors.........................................................         5

Use of Proceeds......................................................         9

Selling Stockholders.................................................         9

Plan of Distribution.................................................        11

Legal Matters........................................................        11

Experts..............................................................        11

================================================================================

================================================================================


                                 283,350 SHARES





                             ASPEN TECHNOLOGY, INC.





                                  COMMON STOCK



                                   ----------
                                   PROSPECTUS
                                   ----------







                                            , 1997

================================================================================
<PAGE>   15
                                     PART II
                     INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14.   OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION

      The following table sets forth the various expenses to be paid by the
Registrant in connection with the issuance and distribution of the shares of
Common Stock being registered. All amounts shown are estimates except for the
Securities and Exchange Commission registration fee. The Registrant will pay all
expenses in connection with the distribution of the shares of Common Stock being
sold by the Selling Stockholders (including fees and expenses of counsel for the
Company), except for any discounts, concessions, commissions or other
compensation due to any broker or dealer in connection with the sale of any of
the shares offered hereby.

<TABLE>
<S>                                                                    <C>
           Securities and Exchange Commission registration fee.....    $2,850
           Legal fees and expenses ................................     1,750
           Printing, EDGAR formatting and mailing expenses ........       500
           Miscellaneous ..........................................       400
                                                                       ------
                Total .............................................    $5,500
                                                                       ======
</TABLE>

ITEM 15.   INDEMNIFICATION OF DIRECTORS AND OFFICERS

      Article 6 of the Company's Restated Articles of Organization provides that
the Company shall indemnify each person who is or was a director, officer,
employee or other agent of the Company, and each person who is or was serving at
the request of the Company as a director, trustee, officer, employee or other
agent of another organization in which it directly or indirectly owns shares or
of which it is directly or indirectly a creditor, against all liabilities, costs
and expenses reasonably incurred by any such persons in connection with the
defense or disposition of or otherwise in connection with or resulting from any
action, suite, or other proceeding in which they may be involved by reason of
being or having been such a director, officer, employee agent or trustee, or by
reason of any action taken or not taken in such capacity, except with respect to
any matter as to which such person shall have been finally adjudicated by a
court of competent jurisdiction not to have acted in good faith in the
reasonable belief that his or her action was in the best interests of the
Company. The provisions of the Company's Articles pertaining to indemnification
may not be amended and no provision inconsistent therewith may be adopted
without the approval of either the Board of Directors or the holders of at least
a majority of the voting power of the Company. Section 67 of Chapter 156B of the
Massachusetts Business Corporation Law authorizes a corporation to indemnify its
directors, officers, employees and other agents unless such person shall have
been adjudicated in any proceeding not to have acted in good faith in the
reasonable belief that such action was in the best interests of the corporation.

      The Company maintains a directors' and officers' insurance policy that
covers certain liabilities of directors and officers of the Company, including
liabilities under the Securities Act. The Company maintains a general liability
insurance policy that covers certain liabilities of directors and officers of
the Company arising out of claims based on acts or omissions in their capacities
as directors or officers.



                                      II-1
<PAGE>   16
ITEM 16.   EXHIBITS

 EXHIBIT NO.
 -----------

     5.1      Opinion of Foley, Hoag & Eliot LLP

    23.1      Consent of Arthur Andersen LLP

    23.2      Consent of Foley, Hoag & Eliot LLP (included in Exhibit 5.1)

    24.1      Powers of Attorney (included on pages II-4 and II-5)

    99.1      Section 5.9 (Registration of Exchanged Shares) of the Agreement
              and Plan of Reorganization dated as of August 1, 1997 between
              Aspen Technology, Inc., AT Acquisition Corp., NeuralWare, Inc. and
              the Stockholders of NeuralWare, Inc.

    99.2      Section 5.9 (Registration of Exchanged Shares) of the Share
              Exchange Agreement dated as of August 28, 1997 between Aspen
              Technology, Inc., The SAST Corporation Limited, Special Analysis
              and Simulation Technology Limited, S.A.S.T. Process Limited,
              Special Analysis and Computing Services Limited, SAST, Inc. and
              the Founders of The SAST Corporation Limited


ITEM 17.   UNDERTAKINGS

      (a)   The undersigned Registrant hereby undertakes:

            (1)   To file, during any period in which offers or sales are being
                  made, a post-effective amendment to this Registration
                  Statement;

                    (i) To include any prospectus required to Section 10(a)(3)
                        of the Securities Act of 1933;

                   (ii) To reflect in the prospectus any facts or events arising
                        after the effective date of the Registration Statement
                        (or the most recent post-effective amendment thereof)
                        which, individually or in the aggregate, represent a
                        fundamental change in the information set forth in the
                        Registration Statement; and

                  (iii) To include any material information with respect to the
                        plan of distribution not previously disclosed in the
                        Registration Statement or any material change to such
                        information in the Registration Statement;

                  provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do
                  not apply if the registration statement is on Form S-3, Form
                  S-8, and the information required to be included in a
                  post-effective amendment by those paragraphs is contained in
                  periodic reports filed by the Registrant pursuant to Section
                  13 or Section 15(d) of the Securities Exchange Act of 1934
                  that are incorporated by reference in this Registration
                  Statement.

            (2)   That, for the purpose of determining any liability under the
                  Securities Act of 1933, each such post-effective amendment
                  shall be deemed to be a new registration statement relating to
                  the securities offered therein, and the offering of such
                  securities at that time shall be deemed to be the initial bona
                  fide offering thereof.

            (3)   To remove from registration, by means of a post-effective
                  amendment any of the securities being registered which remain
                  unsold at the termination of the offering.


                                      II-2
<PAGE>   17
      (b)   The undersigned Registrant hereby undertakes that, for purposes of
            determining any liability under the Securities Act of 1933, each
            filing of the Registrant's annual report pursuant to Section 13(a)
            or Section 15(d) of the Securities Exchange Act of 1934 that is
            incorporated by reference to the Registration Statement shall be
            deemed to be a new registration statement relating to the securities
            offered therein, and the offering of such securities at that time
            shall be deemed to be the initial bona fide offering thereof.

      (c)   Insofar as indemnification for liabilities arising under the
            Securities Act of 1933 may be permitted to directors, officers and
            controlling persons of the Registrant pursuant to the foregoing
            provisions, or otherwise, the Registrant has been advised that in
            the opinion of the Securities and Exchange Commission such
            indemnification is against public policy as expressed in the Act and
            is, therefore, unenforceable. In the event that a claim for
            indemnification against such liabilities (other than the payment by
            the Registrant of expenses incurred or paid by a director, officer
            or controlling person of the Registrant in the successful defense of
            any action, suit or proceeding) is asserted by such director,
            officer or controlling person in connection with the securities
            being registered, the Registrant will, unless in the opinion of its
            counsel the matter has been settled by controlling precedent, submit
            to a court of appropriate jurisdiction the question whether such
            indemnification by it is against public policy as expressed in the
            Act and will be governed by the final adjudication of such issue.


                                      II-3
<PAGE>   18
                                  SIGNATURES

      Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-3 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Cambridge, Commonwealth of Massachusetts, on October
31, 1997.

                            ASPEN TECHNOLOGY, INC.


                            By:             /s/ LAWRENCE B. EVANS
                               ------------------------------------------------
                                                 LAWRENCE B. EVANS
                              Chairman of the Board and Chief Executive Officer


                                POWER OF ATTORNEY

      We, the undersigned officers and directors of Aspen Technology, Inc.,
hereby severally constitute and appoint Lawrence B. Evans, Mary A. Palermo and
Stephen J. Doyle, and each of them singly, our true and lawful attorneys with
full power to them, and each of them singly, to sign for us and in our names in
the capacities indicated below, the Registration Statement on Form S-3 filed
herewith and any and all pre-effective and post-effective amendments to said
Registration Statement, and any subsequent Registration Statement for the same
offering which may be filed under Rule 462(b) under the Securities Act of 1933
and generally to do all such things in our names and on our behalf in our
capacities as officers and directors to enable Aspen Technology, Inc. to comply
with the provisions of the Securities Act of 1933 and all requirements of the
Securities and Exchange Commission, hereby ratifying and confirming our
signatures as they may be signed by our said attorneys, or any of them, to said
Registration Statement and any and all amendments thereto or to any subsequent
Registration Statement for the same offering which may be filed under said Rule
462(b).

      Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and as of the date indicated.


<TABLE>
<CAPTION>
        SIGNATURE                         TITLE                                      DATE
        ---------                         -----                                      ----

<S>                             <C>                                            <C>
  /S/ LAWRENCE B. EVANS
- -----------------------------   Chairman of the Board                          October 31, 1997
    LAWRENCE B. EVANS             and Chief Executive Officer
                                  (Principal Executive Officer)

   /S/ MARY A. PALERMO
- -----------------------------   Executive Vice President, Finance              October 31, 1997
     MARY A. PALERMO              and Chief Financial Officer
                                  (Principal Financial and Accounting Officer)

  /S/ JOSEPH F. BOSTON
- -----------------------------   Director                                       October 31, 1997
    JOSEPH F. BOSTON


/S/ GRESHAM T. BREBACH, JR.
- -----------------------------   Director                                       October 31, 1997
  GRESHAM T. BREBACH, JR.
</TABLE>



                                      II-4
<PAGE>   19
<TABLE>
<S>                             <C>                                          <C>
  /S/ DOUGLAS R. BROWN
- -----------------------------   Director                                     October 31, 1997
    DOUGLAS R. BROWN


   /S/ JOAN C. MCARDLE
- -----------------------------   Director                                     October 31, 1997
     JOAN C. MCARDLE


     /S/ ALISON ROSS
- -----------------------------   Director                                     October 31, 1997
       ALISON ROSS
</TABLE>



                                      II-5

<PAGE>   1
                                                                     Exhibit 5.1



                             FOLEY, HOAG & ELIOT LLP
                             One Post Office Square
                        Boston, Massachusetts 02109-2170
                            Telephone: (617) 832-1000
                            Facsimile: (617) 832-7000
                                  Telex 940693
                               http://www.fhe.com




                               November 4, 1997




ASPEN TECHNOLOGY, INC.
Ten Canal Park
Cambridge, Massachusetts  02141

Ladies and Gentlemen:

      We have acted as special counsel for Aspen Technology, Inc., a
Massachusetts corporation (the "Company"), in connection with the preparation
and filing with the Securities and Exchange Commission under the Securities Act
of 1933, as amended, of a Registration Statement on Form S-3 (the "Registration
Statement") relating to the offering of up to 283,350 shares (the "Shares") of
the Company's common stock, $.10 par value, by certain stockholders of the 
Company.

      In arriving at the opinion expressed below, we have examined and relied on
the following documents:

     (i)   the Registration Statement;

     (ii)  the Articles of Organization of the Company, as amended as of the
           date hereof;

     (iii) the By-Laws of the Company, as amended as of the date hereof; and

     (iv)  minutes of meetings of the Board of Directors of the Company held on
           May 20, 1997 and August 12, 1997.

In addition, we have examined and relied on the originals or copies certified or
otherwise identified to our satisfaction of all such other records, documents
and instruments of the Company and such other persons, and we have made such
investigations of law, as we have deemed appropriate as a basis for the opinions
expressed below. We have assumed the genuineness of all signatures and the
authenticity of all documents submitted to us as originals and the conformity to
the original documents of all documents submitted to us as certified or
photostatic copies.


<PAGE>   2

ASPEN TECHNOLOGY, INC.
November 4, 1997
Page Two


      We express no opinion other than as to the laws of The Commonwealth of
Massachusetts.

      Based upon the foregoing, we are of the opinion that the Shares have been
duly authorized and validly issued and are fully paid and non-assessable.

      We consent to the filing of this opinion as Exhibit 5.1 to the
Registration Statement and to the reference to us under the heading "Legal
Matters" in the prospectus forming a part of the Registration Statement.

                                             Very truly yours,

                                             FOLEY, HOAG & ELIOT LLP



                                             By /s/ MARK L. JOHNSON
                                             ----------------------
                                                A Partner

<PAGE>   1
                                                                    Exhibit 23.1



                    CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS


      As independent public accountants, we hereby consent to the incorporation
by reference in this Registration Statement on Form S-3 of our report included
in the Annual Report on Form 10-K of Aspen Technology, Inc. for the fiscal year
ended June 30, 1997 and to the reference to our firm in this Registration
Statement.



                                                           ARTHUR ANDERSEN LLP

Boston, Massachusetts
November 3, 1997

<PAGE>   1
                                                                    Exhibit 99.1


   [Excerpted from Reorganization Agreement dated as of August 1, 1997 between
                  Aspen Technology, Inc., AT Acquisition Corp.,
             NeuralWare, Inc. and Stockholders of NeuralWare, Inc.]

     5.9. REGISTRATION OF EXCHANGED SHARES.

     (a) HOLDERS AND INITIAL HOLDERS. The rights to registration of shares under
this section is for the Founders, the remaining Stockholders (collectively the
"Initial Holders"), and any of their respective (i) successors-in-interest,  
(ii) family members, trusts wholly or principally for the benefit of family
members and affiliates to whom an Initial Holder or its successor-in-interest
transfers any of the Registrable Securities (as defined in paragraph (b) of
this section) initially issued to such Initial Holder and (iii) any other
person or persons to whom an Initial Holder transfers all or substantially all
of the Registrable Securities initially issued to such Initial Holder, which
family member, trust, affiliate or person described in clause (ii) or (iii) is
registered on the books of AspenTech (together with the Initial Holders, such
successors-in-interest, family members, trusts, affiliates and other persons
are hereinafter sometimes referred to as the "Holders").

     (b) SECURITIES SUBJECT TO THIS SECTION. The securities entitled to the
benefits of this section are the Exchanged Shares and any other securities
issued by AspenTech in exchange for any of the Exchanged Shares (collectively
the "Registrable Securities") but, with respect to any particular Registrable
Security, only so long as it continues to be a Registrable Security. Registrable
Securities shall include any securities issued as a dividend or distribution on
account of Registrable Securities or resulting from a subdivision of the
outstanding shares of Registrable Securities into a greater number of shares (by
reclassification, stock split or otherwise). For the purposes of this Agreement,
a security that was at one time a Registrable Security shall cease to be a
Registrable Security when (i) such security has been effectively registered
under the Securities Act and has been disposed of pursuant to such registration
statement, (ii) such security is or can be distributed to the public pursuant to
Rule 144 (or any similar provision then in force) under the Securities Act,
(iii) such security has been otherwise transferred and (A) AspenTech has
delivered a new certificate or other evidence of ownership not bearing the
legend set forth on the Exchanged Shares upon the initial issuance thereof (or
other legend of similar import) and (B) in the opinion of counsel to AspenTech,
the subsequent disposition of such security shall not require the registration
or qualification under the Securities Act or (C) such security has ceased to be
outstanding.

     (c) SHELF REGISTRATION. AspenTech agrees that it shall cause to be filed a
registration statement (the "Shelf Registration") on Form S-3 or any other
appropriate form under the Securities Act for an offering to be made on a
delayed or continuous basis pursuant to Rule 415 thereunder or any similar rule
that may be adopted by the Securities and Exchange Commission (the "Commission")
and permitting sales in ordinary course brokerage or dealer transactions not
involving an underwritten public offering (and shall register or qualify the
shares to be sold in such offering under such other securities or "blue sky"
laws as would reasonably be required) covering the entire issue of Exchanged
Shares and such other shares of Aspen Common as may be included pursuant to
registration rights of other holders of Aspen Common. AspenTech shall use its
best efforts to (i) cause the Shelf Registration to be declared effective by the
Commission on, or as soon as practicable after, the date on which AspenTech
first publishes financial results covering at least thirty days of
post-acquisition combined operations of AspenTech and NeuralWare and (ii) keep
the Shelf Registration continuously effective (and register or qualify the
shares to be sold in such offering under such other securities or "blue sky"
laws as would be required for a period (the "Shelf Registration Period") of
ninety (90) days after the date on which the Shelf Registration is declared
effective 

<PAGE>   2

by the Commission (or such shorter period that will terminate when all Exchanged
Shares covered by the Shelf Registration have been sold). AspenTech agrees, if
necessary, to supplement or make amendments to the Shelf Registration, if
required by the registration form used by AspenTech for the Shelf Registration
or by the instructions applicable to such registration form or by the Securities
Act or the rules or regulations thereunder.

         (d) EXPENSES. AspenTech shall pay all expenses incident to its
performance of or compliance with this Section, regardless of whether such
registration becomes effective, including (i) all Commission, stock exchange or
market registration and filing fees, (ii) all fees and expenses incurred in
complying with securities or "blue sky" laws (including reasonable fees and
disbursements of counsel in connection with "blue sky" qualifications of the
Registrable Securities), (iii) all printing, messenger and delivery expenses,
(iv) all fees and disbursements of AspenTech's independent public accountants
and counsel and (v) all fees and expenses of any special experts retained by
AspenTech in connection with any registration pursuant to the terms of this
Agreement; provided, however, that the Holders shall be liable for (A) any fees
or commissions of brokers, dealers or underwriters, (B) any transfer taxes and
(C) any fees or expenses of consultants, financial advisors, counsel and other
professionals acting on behalf of the Holders in connection with any
registration pursuant to the terms of this Agreement.


[For purposes of the foregoing Section 5.9, the following terms have the
indicated meanings:

"Aspen Common" means Aspen common stock, $.10 par value.

"AspenTech" means Aspen Technology, Inc.

"Exchanged Shares" means the shares of Aspen Common exchanged for the previously
outstanding shares of common stock of NeuralWare, Inc.

"NeuralWare" means NeuralWare, Inc

"Securities Act" means the Securities Act of 1933, as amended.]


<PAGE>   1
                                                                    Exhibit 99.2


  [Excerpted from Reorganization Agreement dated as of August 28, 1997 between
   Aspen Technology, Inc., The SAST Corporation Limited, Special Analysis and
            Simulation Technology Limited, S.A.S.T. Process Limited,
         Special Analysis and Computing Services Limited, SAST, Inc. and
                    Founders of The SAST Corporation Limited]

     5.9. REGISTRATION OF EXCHANGED SHARES.

     (a) HOLDERS AND INITIAL HOLDERS. The rights to registration of shares under
this section are for the Founders, and any of their respective (i) successors-
in-interest, (ii) family members, trusts wholly or principally for the benefit
of family members and affiliates to whom a Founder or its successor-in-interest
transfers any of the Registrable Securities (as defined in paragraph (b) of
this section) initially issued to such Founder and (iii) any other person or
persons to whom a Founder transfers all or substantially all of the Registrable
Securities initially issued to such Founder, which family member, trust,
affiliate or person described in clause (ii) or (iii) is registered on the
books of AspenTech (together with the Founders, such successors-in-interest,
family members, trusts, affiliates and other persons are hereinafter sometimes
referred to as the "Holders").

     (b) SECURITIES SUBJECT TO THIS SECTION. The securities entitled to the
benefits of this section are the Exchanged Shares and any other securities
issued by AspenTech in exchange for any of the Exchanged Shares (collectively
the "Registrable Securities") but, with respect to any particular Registrable
Security, only so long as it continues to be a Registrable Security. Registrable
Securities shall include any securities issued as a dividend or distribution on
account of Registrable Securities or resulting from a subdivision of the
outstanding shares of Registrable Securities into a greater number of shares (by
reclassification, stock split or otherwise). For the purposes of this Agreement,
a security that was at one time a Registrable Security shall cease to be a
Registrable Security when (i) such security has been effectively registered
under the Securities Act and has been disposed of pursuant to such registration
statement, (ii) such security is or can be distributed to the public pursuant to
Rule 144 (or any similar provision then in force) under the Securities Act,
(iii) such security has been otherwise transferred and (A) AspenTech has
delivered a new certificate or other evidence of ownership not bearing the
legend set forth on the Exchanged Shares upon the initial issuance thereof (or
other legend of similar import) and (B) in the opinion of counsel to AspenTech,
the subsequent disposition of such security shall not require the registration
or qualification under the Securities Act or (C) such security has ceased to be
outstanding.

     (c) SHELF REGISTRATION. AspenTech agrees that it shall cause to be filed a
registration statement (the "Shelf Registration") on Form S-3 or any other
appropriate form under the Securities Act for an offering to be made on a
delayed or continuous basis pursuant to Rule 415 thereunder or any similar rule
that may be adopted by the Securities and Exchange Commission (the "Commission")
and permitting sales in ordinary course brokerage or dealer transactions not
involving an underwritten public offering (and shall register or qualify the
shares to be sold in such offering under such other securities or "blue sky"
laws as would reasonably be required) covering the entire issue of Registrable
Securities and such other shares of Aspen Common as may be included pursuant to
registration rights of other holders of Aspen Common. AspenTech shall use its
best efforts to (i) cause the Shelf Registration to be declared effective by the
Commission on, or as soon as practicable after, the date on which AspenTech
first publishes financial results covering at least thirty days of
post-acquisition combined operations of AspenTech and the SAST Companies and
(ii) keep the Shelf Registration continuously effective (and register or qualify
the shares to be sold in such offering under such other securities or "blue sky"
laws as would be required for a period 

<PAGE>   2

(the "Shelf Registration Period") of ninety (90) days after the date on which
the Shelf Registration is declared effective by the Commission (or such shorter
period that will terminate when all Registrable Securities covered by the Shelf
Registration have been sold). AspenTech agrees, if necessary, to supplement or
make amendments to the Shelf Registration, if required by the registration form
used by AspenTech for the Shelf Registration or by the instructions applicable
to such registration form or by the Securities Act or the rules or regulations
thereunder.

     (d) PIGGYBACK REGISTRATION, At any time prior to the first anniversary of
the date hereof, whenever AspenTech proposes to file a registration statement
under the Securities Act with respect to a public offering of Aspen Common for
cash sale by AspenTech for its own account or by any of AspenTech's
securityholders, AspenTech shall give written notice (the "Offering Notice") of
such proposed filing to each of the Holders at least thirty days before the
anticipated filing date. Such Offering Notice shall offer all such Holders the
opportunity to register such number of Registrable Securities as each such
Holder may request in writing, which request for registration (each, a
"Piggyback Registration") must be received by AspenTech within fifteen days
after the Offering Notice is given. AspenTech shall use all reasonable efforts
to cause the managing underwriter or underwriters of a proposed underwritten
offering to permit the holders of the Registrable Securities requested to be
included in the registration for such offering to include such Registrable
Securities in such offering on the same terms and conditions as the shares of
Aspen Common included therein. Notwithstanding the foregoing, if the managing
underwriter or underwriters of a proposed underwritten offering advise AspenTech
in writing that in its or their opinion the number of Registrable Securities
proposed to be sold in such offering exceeds the number of Registrable
Securities that can be sold in such offering without adversely affecting the
market for Aspen Common, AspenTech will not be required to include in such
registration the number of Registrable Securities, if any, to be offered for the
accounts of Holders or, in AspenTech's discretion, it may include such
Registrable Securities of Holders but such Registrable Securities, shall be
reduced pro rata on the basis of the relative number of any Registrable
Securities requested by each such Holder to be included in such registration to
the extent necessary to reduce the total number of Registrable Securities to be
included in such offering to the number recommended by such managing underwriter
or underwriters.

     (e) EXPENSES. AspenTech shall pay all expenses incident to its performance
of or compliance with this Section 5.9, regardless of whether such registration
becomes effective, including (i) all Commission, stock exchange or market
registration and filing fees, (ii) all fees and expenses incurred in complying
with securities or "blue sky" laws (including reasonable fees and disbursements
of counsel in connection with "blue sky" qualifications of the Registrable
Securities), (iii) all printing, messenger and delivery expenses, (iv) all fees
and disbursements of AspenTech's independent public accountants and counsel and
(v) all fees and expenses of any special experts retained by AspenTech in
connection with any registration pursuant to the terms of this Agreement;
provided, however, that the Holders shall be liable for (A) any fees or
commissions of brokers, dealers or underwriters, (B) any transfer taxes and 
(C) any fees or expenses of consultants, financial advisors, counsel and other
professionals acting on behalf of the Holders in connection with any
registration pursuant to the terms of this Agreement.


[For purposes of the foregoing Section 5.9, the following terms have the
indicated meanings:

"Aspen Common" means Aspen common stock, $.10 par value.

"AspenTech" means Aspen Technology, Inc.


<PAGE>   3

"Exchanged Shares" means the shares of Aspen Common exchanged for the previously
outstanding shares of common stock of the SAST Companies.

"SAST Companies" means The SAST Corporation Limited and all its majority-owned
subsidiaries.

"Securities Act" means the Securities Act of 1933, as amended.]


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