Release Details

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Sept. 14, 2005-- Aspen Technology, Inc. (Nasdaq: AZPN) today announced that Lyondell Chemical Company (NYSE: LYO), a major global manufacturer of ethylene, propylene and polyethylene, is the latest in a growing list of companies to have selected the Aspen Apollo(TM) non-linear advanced control solution for the polymers industry. Aspen Apollo is being implemented by Lyondell's Equistar Chemicals business at its La Porte, Texas, complex where it will enable the company to optimize execution of product transitions and improve steady-state quality performance.

"AspenTech combines deep domain expertise with best-in-class polymer modeling and control technology," said Rick Fontenot, vice president of manufacturing services for Lyondell. "Implementing the Aspen Apollo solution will enable us to improve performance in both transition and steady-state conditions, and will support our overall drive to satisfy our customers through the delivery of consistent, high-quality products."

Lyondell is the thirteenth company to select Aspen Apollo since 2003. The solution has been applied to a broad range of the leading polymer process technologies, and has delivered faster product transitions, reduced quantities of off-specification material and a significant increase in production capacity.

"Aspen Apollo has achieved widespread success since its launch," said Steve Pringle, senior vice president global services, AspenTech. "Lyondell is recognized as a global leader in the polymers industry, and its decision to select our advanced control solution reflects the significant added value this innovative technology can deliver to polymer producers, which has already resulted in proven benefits such as optimal manufacturing operations and a greater agility to respond to market demand."

AspenTech developed the Aspen Apollo non-linear controller specifically for the highly complex behavior which is unique to polymer processes. Additionally, the widespread deployment of the solution among a variety of companies has reinforced AspenTech's position as one of the leading providers of advanced control solutions to the polymer industry. The combination of in-depth polymer operational know-how, best-in-class technology, experienced global implementation teams and industry-recognized customer support provides customers with an unrivalled advanced control solution for polymers.

Aspen Apollo is a key component of aspenONE(TM) Advanced Process Control for Polymers, AspenTech's integrated solution for the polymers industry which enables companies to manage and optimize the operational performance of their production facilities.

About Lyondell

Lyondell Chemical Company, headquartered in Houston, Texas, is North America's third-largest independent, publicly traded chemical company. Lyondell is a major global manufacturer of basic chemicals and derivatives including ethylene, propylene, titanium dioxide, styrene, polyethylene, propylene oxide and acetyls. It also is a significant producer of gasoline blending components. The company has a 58.75 percent interest in LYONDELL-CITGO Refining LP, a refiner of heavy, high-sulfur crude oil. Lyondell is a global company operating on five continents and employs approximately 10,000 people worldwide. Equistar Chemicals is a wholly-owned subsidiary of Lyondell.

About AspenTech

Aspen Technology, Inc. provides industry-leading software and professional services that help process companies improve efficiency and profitability by enabling them to model, manage and control their operations. The new generation of integrated aspenONE(TM) solutions are aligned with the key industry business processes, providing manufacturers the capabilities they need to optimize operational performance, make real-time decisions and synchronize the plant and supply chain. Over 1,500 leading companies already rely on AspenTech's software, including Bayer, BASF, BP, ChevronTexaco, DuPont, ExxonMobil, Fluor, GlaxoSmithKline, Sanofi-Aventis, Shell, and Total. For more information, visit www.aspentech.com.

This press release may contain forward-looking statements for purposes of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Actual results may vary significantly from AspenTech's expectations based on a number of risks and uncertainties, including, without limitation: AspenTech's plan to improve operational performance may not be implemented effectively; AspenTech has identified material weaknesses in its internal controls with respect to software license revenue recognition and other matters, that, if not remedied effectively, could result in material misstatements; risks around securities litigation and investigations; AspenTech's lengthy sales cycle makes it difficult to predict quarterly operating results; fluctuations in AspenTech's quarterly operating results; AspenTech's dependence on customers in the cyclical chemicals, petrochemicals and petroleum industries; the possibility of new accounting standards or the interpretation of existing accounting standards affecting our financial results; AspenTech's ability to raise additional capital as required; intense competition; AspenTech's need to develop and market products successfully; reliance on relationships with strategic partners; challenges associated with international operations; and other risk factors described from time to time in AspenTech's periodic reports filed with the Securities and Exchange Commission. AspenTech cannot guarantee any future results, levels of activity, performance, or achievements. AspenTech expressly disclaims any current intention to update forward-looking statements after the date of this press release.

AspenTech, aspenONE, Aspen Apollo and the aspen leaf logo are trademarks of Aspen Technology, Inc., Cambridge, Mass.

CONTACT:
For Media:
Aspen Technology, Inc.
Robin Swanger, 281-504-3256
robin.swanger@aspentech.com

Lyondell Chemical Company
Eric Stebel, 713-309-3987
eric.stebel@lyondell.com

For Investors:
Aspen Technology, Inc.
Joshua Young, 617-949-1274
joshua.young@aspentech.com