ATG and Steria Announce Today a Wide Ranging Partnership Agreement Focused Upon Delivering Consulting and Services in Support of ATG's European Business.

CAMBRIDGE, Mass. -- ATG (Art Technology Group, Inc. NASDAQ: ARTG), whose licensed and on demand technology powers e-commerce sites and corresponding e-marketing and customer service for the world's most customer-centric enterprises, and Steria, one of Europe's leading IT systems integration and consulting services businesses, today announced the signing of a wide ranging partnership agreement focused upon delivering consulting and services in support of ATG's European business.

Peter Ford, ATG Alliances Director for Europe, Middle East & Africa said, "We're delighted to have secured the services of Steria to assist in delivering our solutions across Europe. The partnership will offer Steria customers the opportunity to extend their existing CRM infrastructure and significantly enhance online customer experience and support services using ATG's solutions."

Gilles Graziani, Director at Steria said, "We see this alliance with ATG as a strategic decision to provide our clients with time-to-market world class solutions in customer experience and selfcare. ATG's solutions will help our clients to better understand how end users interact with the business at every touch point and allow them to improve the potential value of every customer interaction, whether it is an outbound marketing campaign, a commerce transaction, or a request for service support. This partnership brings real value in our Client - Facing set of solutions and we are excited to working with ATG across Europe."

About Steria (www.steria.com)

Extensive expertise in its three core businesses of consulting, systems integration and managed services has made Steria a leading end-to-end IT services provider for companies and public authorities throughout Europe. With a revenue of EUR 1.2 billion and 9,300 employees, Steria is one of the top ten European IT services companies.

Understanding the challenges facing its customers enables Steria to design business-specific solutions with high added value in all of its fields of expertise - the public sector, healthcare, banking/insurance, telecommunications and utilities/transport/manufacturing - as well as innovative technological solutions. Based on over 35 years' experience in managing large-scale projects, an exceptional ability to respond and an industrial approach to business, Steria has developed a result-based culture with a commitment to service quality and customer satisfaction. Steria's employees, who hold 24% of the Group's capital, draw on its core values of simplicity, creativity, independence, respect and openness to transform the latest technology into added-value services, enabling Steria to help its customers achieve and maintain competitive advantage. Steria is listed on Euronext Paris, Eurolist (Compartment B).

About ATG

ATG (Art Technology Group, Inc., NASDAQ: ARTG) makes the software that the world's most customer-conscious companies use to create a more relevant and consistent customer experience, throughout the marketing, commerce, and service lifecycle, and across the Web, e-mail, call center, and mobile channels. Offering an alternative to the traditional silo-based approach to customer-facing applications, ATG Wisdom(TM) is the company's strategy for delivering a seamless, more compelling, and mutually valuable experience to each customer and segment. The company fulfills this strategy by providing fully integrated best-of-breed product suites installed on-premise or delivered on-demand. ATG's solutions power over 600 major brands, including A&E Networks, Airbus, American Airlines, American Eagle Outfitters, Best Buy, Boeing, Cingular Wireless, DirecTV, France Telecom, Friends Provident, Hewlett-Packard, Hotels.com, Hyatt Hotels, HSBC, InterContinental Hotels Group, Kingfisher, Louis Vuitton, Merrill Lynch, Neiman Marcus, Philips, Procter & Gamble, Symantec, T-Mobile, Target, US Army, US Navy, Warner Music, and Wells Fargo. The company is headquartered in Cambridge, Massachusetts, with additional locations throughout North America and Europe. For more information about ATG, please visit www.atg.com.

(C) 2006 Art Technology Group, Inc. ATG and Art Technology Group are registered trademarks, and ATG Wisdom is a trademark of Art Technology Group, Inc. All other product names, service marks, and trademarks mentioned herein are trademarks of their respective owners.

This press release contains forward-looking statements for purposes of the safe harbor provisions under The Private Securities Litigation Reform Act of 1995. These statements involve known and unknown risks and uncertainties that may cause ATG's actual results, levels of activity, performance or achievements to be materially different from any future results, levels of activity, performance or achievements expressed or implied by such forward-looking statements. Important risk factors affecting ATG's business generally may be found in its periodic reports and registration statements filed with the Securities and Exchange Commission at www.sec.gov . Risk factors related to the subject matter of this press release include the possibility that the ATG product deployment will not be successful, on time or significantly enhance the user's Internet experience or will not increase customer revenue across brands; that those customers leveraging ATG will not have the opportunity to increase revenue and decrease future costs; the need to adapt to rapid changes so products do not become obsolete; the possibility of errors in ATG's software products; the possibility that the solution will not make customer implementations faster or more flexible or permit the customer to meet its customer-facing or infrastructure requirements; that the ATG product will not continue to be integrated with third party applications servers or will not support all Web services enabled systems; that ATG's product strategy may change in the future; and the risks and costs of intellectual property litigation. ATG undertakes no obligation to update any of the forward-looking statements after the date of this press release.