Avistar Announces Patent Infringement Lawsuit Against TANDBERG; Suit Alleges Unlawful Use of Fundamental Videoconferencing Technologies.

REDWOOD SHORES, Calif. -- Avistar Communications Corporation (Nasdaq:AVSR), a provider of business video collaboration solutions and technology, today announced that its wholly owned subsidiary, Collaboration Properties, Inc. (CPI), has filed a patent infringement lawsuit against TANDBERG ASA and TANDBERG, Inc. In the suit, CPI alleges that several TANDBERG videoconferencing products infringe three of CPI's patents. The three patents involved are U.S. Patent No. 5,867,654; No. 5,896,500; and No. 6,212,547. The suit was filed in the U.S. District Court for the Northern District of California by the law firm of Simpson Thacher & Bartlett LLP.

These three patents cover key technologies, some of which are fundamental to interactive video calling:

--video and data conferencing over unshielded twisted pair (UTP) networks;

--distributed call-state management; and

--separate monitors for simultaneous computer-based data and videoconferencing.

Avistar developed these technologies as core components of its networked architecture and the AvistarVOS(TM) video operating system, an open software platform that delivers video communication services. In the suit, CPI alleges that several TANDBERG products, including room-based and desktop videoconferencing systems, employ some or all of these technologies.

"Currently, we hold a portfolio of 67 issued patents worldwide, with many other pending patent applications, covering the core videoconferencing functionalities and architectures that are part of the AvistarVOS software and fundamental to Avistar's networked video communication products," said William L. Campbell, CEO of CPI. "For more than three years we have made these patents available for licensing because we want the videoconferencing industry to work in concert with Avistar to bring easy, open, global video communication to every professional. During that time we have asserted our patents in court and have licensed them. In this case, it has become important that CPI take action to protect the integrity of its intellectual property and establish appropriate licensing arrangements."

Avistar CEO Gerald J. Burnett said, "For twelve years Avistar has been investing time and money in the development of a video application suite and platform technology necessary for reliable, high-quality, self-service video applications. Our goal has been to video-enable business, going well beyond traditional videoconferencing, by integrating video into where and how people work. We believe there is room for many companies who would like to take part in the tremendous growth prospects of converged, video-enabled business -- the vBusiness world."

The AvistarVOS enterprise video software and networked video infrastructure provide professionals with a full range of standards-based video communication services -- two-way and multi-party calling, record and playback, video-on-demand, video publishing, interactive broadcast origination -- all provided directly from end-point desktops and rooms. CPI patents technologies in synchronization with and in advance of Avistar products and makes its collaborative video intellectual property available to potential partners through licensing. Inquiries regarding CPI's licensing may be directed to Stephanie Neutz, Esq. at [phone].

About Avistar Communications Corporation

Avistar Communications Corporation develops, markets, and supports a video collaboration platform for the enterprise, all powered by the AvistarVOS(TM) software. From the desktop, Avistar delivers TV-quality video calling, recording, publishing to web and emails, video-on-demand, broadcast origination and distribution, and document sharing. Avistar video-enables business processes by integrating visual communications into the daily workflow and connecting communities of users within and across enterprises. Founded in 1993, Avistar is headquartered in Redwood Shores, California, with sales offices in New York and London. Avistar's technology is used in more than 35 countries.

Collaboration Properties, Inc. (CPI), a wholly owned subsidiary of Avistar, holds a current portfolio of 67 patents for inventions in the primary areas of video and network technology. CPI pursues patents for presence-based interactions, desktop video, recorded and live media at the desktop, multimedia documents, data sharing, and a rich-service network video architecture to support Avistar's product suite and customers. CPI licenses its patent portfolio and Avistar's video-enabling technologies to companies in the video conferencing, rich-media services, public networking, and related industries.

For more information, visit www.avistar.com.

Forward Looking Statements

Statements made in this news release that are not purely historical, including but not limited to statements regarding the growth prospects of converged, video-enabled business and CPI's prospects for protecting the integrity of its intellectual property and establishing appropriate licensing arrangements, are forward-looking statements within the meaning of Section 21E of the Securities Exchange Act. Such statements are subject to risks and uncertainties that could cause actual results to differ materially, including such factors, among others, as challenges associated with protecting intellectual property in the video communications industry, market acceptance of video-enabled business products, increased competition and technical limitations on the development and application of video collaboration products. These and other risk factors are discussed in Avistar's Annual Report on Form 10-K and Quarterly Reports on Form 10-Q filed with the Securities and Exchange Commission from time to time. Avistar disclaims any intent or obligation to update these forward-looking statements.

Copyright (c) 2005 Avistar Communications Corporation. All rights reserved. Avistar, AvistarVOS, and the Avistar logo are trademarks or registered trademarks of Avistar Communications Corporation.