First Optimization Engine for .NET Enables Faster Business Decision Making and Planning

PARIS and MOUNTAIN VIEW, Calif.- December 2, 2003 –ILOG® (NASDAQ: ILOG; Euronext: ILO, ISIN: FR0004042364), a leading provider of enterprise-class software components and services, today unveiled the latest version of its market-defining optimization software, ILOG CPLEX® 9.0 which includes support for .NET. The new release, the first of its kind for .NET, will enable users to build and deploy optimization applications using any .NET supported language, including Microsoft� Visual Basic® and C#.

ILOG CPLEX, the world's most widely deployed optimization software, improves business efficiency and decision making by allowing businesses to calculate the best utilization of existing resources and implement an action plan that can deliver millions of dollars in savings. In addition to support for .NET, new features in ILOG CPLEX 9.0 include performance enhancements that will further speed decision-making in industries with real-time response requirements, such as transportation logistics, supply chain execution and financial asset management. For instance, a new feature in ILOG CPLEX 9.0, quadratically constrained programming (QCP), provides financial planners with a powerful way to significantly limit risk while maximizing returns because it enables them to utilize a math-based, quantitative approach to portfolio management that extends their control over mitigating risk factors.

ILOG CPLEX 9.0 also includes additional ease of use and performance enhancements, including constraint modeling capabilities that enable linear and logical constraints to be combined in complex applications, enabling the user to develop decision support systems faster by providing a more natural way of describing their model. ILOG CPLEX 9.0 also provides an advanced analysis tool that allows users, when faced with infeasible models, to quickly and easily locate the cause of a problem.

ILOG CPLEX users, numbering in the thousands worldwide, recognize the product for pioneering the industry's fastest and most robust math-programming based optimizers, which are used to solve complex, real-world optimization challenges in industries including manufacturing, transportation, defense and finance. CPLEX 9.0 is more than 40 percent faster than the previous version, already the fastest and most robust optimization engine on the market.

ILOG CPLEX features ILOG Concert Technology™ as the language interface, providing users with the choice of writing applications in Java, C++ and now .NET supported languages. ILOG CPLEX, which can be deployed almost immediately, is an easily embeddable, standards-based software component, making it easy to integrate with legacy systems.

About ILOG
ILOG's innovative enterprise-class software components and services have helped companies maximize their business agility and improve operating efficiency for over 10 years. Over 1000 global corporations and more than three hundred leading software vendors rely on ILOG's business rules, optimization and visualization technologies to achieve dramatic returns on investment, create market-defining products and services, and sharpen their competitive edge. For more details, please visit www.ilog.com.

ILOG and CPLEX are registered trademarks, and ILOG Concert Technology is a trademark, of ILOG. Microsoft and Microsoft Visual Basic are registered trademarks of Microsoft. All other company and product names are trademarks or registered trademarks of their respective owners.

Forward-looking Information
This release contains "forward-looking" information within the meaning of the United States Securities laws that involve risks and uncertainties that could cause actual results to differ materially from those in the forward-looking statements. Potential risks and uncertainties include, without limitation, the success of ILOG CPLEX 9.0 in the .NET marketplace and those risks and uncertainties mentioned under "Risk Factors" in the company's form 20-F for the year ended June 30, 2003, which is on file with the United States Securities and Exchange Commission.