ATG Ranked As A Commerce Platform Leader by Premier Independent Research Firm's "Commerce Platform Wave"

Strong marketing campaign tools, process management, and cross channel customer experience capabilities called out as key differentiators

CAMBRIDGE, Mass., May 3, 2005 - ATG (Art Technology Group, Inc., NASDAQ: ARTG) the software provider behind the most consistent and relevant marketing, commerce, and service experiences, today announced that it has been positioned as a leader in Forrester Research's "Forrester Wave™: Commerce Platforms, Q2, 2005." The report is further evidence that ATG continues to be a leader in the commerce platform market in terms of features, functionality, and product strategy. ATG scored the highest in overall "current product offering," which includes product architecture, customer management, and sales and marketing, among other categories. ATG also scored the highest in "product strategy."

ATG was among the highly select group of "top" commerce platform vendors invited to participate in the evaluation. In this report, ATG was recognized for its focus on delivering rich personalization capabilities, its strong customer data management features, and ultimately, ATG's understanding of the BtoC sellers' goal of providing consistent customer experiences across channels.

According to the report authored by Forrester analyst Tamara Mendelsohn, ATG Commerce is an "especially good fit for buyers that want to put the pedal to the metal. The product can go fast and far with its marketing capabilities and…ATG provides tools to create intricate marketing campaigns and robust A/B split testing features to measure the efficacy of campaigns and creative."¹

Further, Forrester tells readers that the product is ideal for sellers that "want to take personalization to the next level. ATG gathers both implicit and explicit customer data and uses it to segment buyers for personalization - everything from the look and feel of the site to customized marketing creative and offers. ATG's Adaptive Scenario Engine, a graphical process modeler, is a strong tool for creating one-to-one experiences by giving business users the ability to design flexible process flows like the checkout process or marketing campaigns."¹

Finally, in relation to overall product strategy, the report states that "ATG understands retailers' dreams of consistent customer experience across channels and the importance of continuity as shoppers move from one channel to another. The vendor has oriented its roadmap around these concepts…ATG has significant experience in this market with an already highly specialized product as a solid foundation to build on."²

"ATG is a pioneer in the commerce platform market, and we're thrilled that Forrester has recognized our strong heritage and leading market presence in e-marketing and e-commerce," said Cliff Conneighton, senior vice president of marketing, ATG. "At ATG, we're committed to continually evolving and pushing the innovation envelope of what is already considered the finest of commerce platforms. We are dedicated to meeting customer demand now, and in the future."

To view the Forrester Commerce Wave, visit: http://www.atg.com/en/pages/campaigns/forrester/commerce_regform.jhtml

About Forrester Research
Forrester is an independent technology research company that provides pragmatic and forward-thinking advice about technology's impact on business. Business, marketing, and IT professionals worldwide collaborate with Forrester to align their technology investments with their business goals. Forrester offers products and services in four major areas: Research, Data, Consulting, and Community. Established in 1983, Forrester is headquartered in Cambridge, Mass. www.forrester.com

1. "Forrester Wave™: Commerce Platforms, Q2, 2005," April 2005
2. "Forrester Commerce Platforms Scorecard Summary: ATG," April 2005

About ATG
ATG (Art Technology Group, Inc., NASDAQ: ARTG) delivers innovative software to help high-end consumer-facing companies create a richer, more adaptive interactive experience for their customers and partners online, via email and messaging, and through contact centers. ATG has delivered category-leading commerce, marketing and customer service solutions to hundreds of the world's best-known brands including American Eagle Outfitters, Best Buy, Kingfisher, Neiman Marcus, Target, Friends Provident, Merrill Lynch, Wells Fargo, HSBC, A&E Networks, Warner Music, AT&T Wireless, T-Mobile, SBC, Yahoo!, France Telecom, Airbus, GE, Boeing, Philips, Procter & Gamble, Hewlett-Packard, American Airlines, InterContinental Hotels Group, US Army, and US Federal Aviation Administration. The company is headquartered in Cambridge, Massachusetts, with additional locations throughout North America, Europe, and Asia. For more information about ATG, please visit www.atg.com.

© 2005 Art Technology Group, Inc. ATG and Art Technology Group are registered trademarks of Art Technology Group, Inc. All other product names, service marks, and trademarks mentioned herein are trademarks of their respective owners.

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This press release contains forward-looking statements for purposes of the safe harbor provisions under The Private Securities Litigation Reform Act of 1995. Any forward-looking statements contained in this release are based on current expectations, are not guarantees of future performance and are subject to a number of 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. Risk factors related to the subject matter of this press release include the following: the possibility that ATG's product strategy may change; the need to adapt to rapid changes so ATG products do not become obsolete; the possibility of errors in ATG's products; risk that ATG products will not deliver significant and definable business benefits to end users; difficulties encountered in the integration, deployment, or implementation of the ATG products and customers systems; failure in the customer's widespread adoption and use of the ATG products; risk resulting from new product introductions and customer acceptance of new ATG products; fluctuations in customer demand; use of the Internet as a vehicle for ATG products; risks associated with competition and the rapid consolidation of competitors; the ability of ATG to manage its growth and integration efforts and the ability of ATG to compete successfully in the future; non-responsiveness of the market to receipt of awards; the company may not qualify it to be included in future awards or may not receive future awards; costs and risks associated with intellectual property infringement and litigation, as well as other important risk factors affecting ATG's business generally may be found in ATG's periodic reports and registration statements filed with the Securities and Exchange Commission, including but not limited to those appearing under the caption "RISK FACTORS THAT MAY AFFECT RESULTS". ATG undertakes no obligation to update any of the forward-looking statements after the date of this press release.

Tucker Walsh
ATG
+1.617.386.1159
twalsh@atg.com