ATG Selected to Participate in DEMOfall 2005 Conference; ATG to Unveil New Strategy and Application Suite at Industry's Leading Showcase for Technology Innovation.

CAMBRIDGE, Mass. -- ATG (Art Technology Group, NASDAQ: ARTG), the software provider behind the most consistent and relevant marketing, commerce, and customer service experiences, today announced that it has been selected to participate in DEMOfall 2005, one of the world's premier forums for new technology innovation. At the upcoming event, to be held September 19-21 at the Hyatt Regency Resort and Spa in Huntington Beach, Calif., ATG will unveil a groundbreaking new strategy and suite of applications with the intent to revolutionize customer service.

"ATG is among the very few companies chosen to participate in DEMOfall, selected from among hundreds of rigorously screened nominees from around the world," said Chris Shipley, executive producer, DEMOfall 2005. "At DEMOfall, the industry will see only the most significant, relevant and viable technologies and companies. To that end, ATG has created a unique strategy and suite of service applications that will transform and improve the way companies service and support their customers. I look forward to seeing the latest technology advancements ATG will bring to market at our upcoming fall conference."

For 15 years, DEMO conferences have been dedicated to the discovery of major trends and useful tools in enterprise and consumer technology. At DEMOfall, 70 hand-picked hardware and software products will be unveiled for the first time in North America. The insider audience attending DEMO is guaranteed to gain new insight into the future of the industry through first-hand looks at the companies and products that are fueling the next wave of computing.

"ATG is privileged to be among the exclusive set of companies invited to this prestigious industry event," said Bob Burke, president, chief executive officer, and director, ATG. "We believe that our new, branded strategy and unified suite of applications represent a significant advancement in the e-service industry - an advancement that will enable enterprises to deliver much greater value to their customers, and enjoy the benefits of stronger relationships. We are eagerly looking forward to unveiling these exciting new developments at DEMOfall 2005."

About DEMOfall 2005

The annual DEMO conferences focus on emerging technologies and new products, which are hand-selected from across the spectrum of the technology marketplace. The DEMO conferences have earned their reputation for consistently identifying tomorrow's cutting-edge technologies, and have served as launch pad events for companies such as Palm, E*Trade, Handspring and U.S. Robotics, helping them secure venture funding, establish critical business relationships and influence early adopters. Each DEMO conference features approximately 70 new companies, products and technologies. For more information on the DEMO conferences, visit www.demo.com.

About ATG

ATG (Art Technology Group, Inc., NASDAQ: ARTG) makes the software that the world's largest and most prestigious companies use to create a relevant and consistent customer experience, across the Web, e-mail, call center, and mobile channels; and throughout the marketing, commerce, and service lifecycle. With ATG, world-class enterprises create and manage highly targeted online commerce and marketing campaigns, as well as loyalty-driving and cost effective knowledge management, customer service, and support initiatives. ATG's solutions power brands including A&E Networks, Airbus, American Airlines, American Eagle Outfitters, AT&T Wireless, Best Buy, Boeing, France Telecom, Friends Provident, General Electric, Hewlett-Packard, HSBC, InterContinental Hotels Group, Kingfisher, Merrill Lynch, Neiman Marcus, Philips, Procter & Gamble, SBC, T-Mobile, Target, US Army, US Federal Aviation Administration, Warner Music, Wells Fargo, and Yahoo! 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.

(C) 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.

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 their 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 products will transform and improve the way companies service and support their customers represent a significant advancement in the e-service industry and enable enterprises to deliver much greater value to their customers. ATG undertakes no obligation to update any of the forward-looking statements after the date of this press release.