Avici Provides Third Quarter Revenue Outlook

N. Billerica, MA, September 27, 2004 —Avici Systems Inc. (NASDAQ: AVCI), today announced that it expects gross revenues for its third quarter ending September 30, 2004 will be in the range of $3.0 million to $4.0 million. As a result, the Company said it does not expect to achieve its target of 20-30% annual revenue growth in 2004.

The revenue shortfall results from delays in anticipated network build outs and timing of expected orders.

Steve Kaufman, President and CEO said, "We are clearly disappointed with this quarter's revenue level. At the same time, we see our growth prospects strengthening in the coming year as a result of continued progress with our emerging channel business and new customer opportunities."

The Company expects to report its third quarter earnings on October 21, 2004.

About Avici Systems
Avici Systems Inc., headquartered in North Billerica, Mass., is a leading provider of purpose-built carrier-class routing solutions for the Internet. Avici's family of routers is designed to meet carrier requirements for the highest scalability, reliability and network availability, while lowering the total cost of building and operating their networks. The company's routing systems provide new IP solutions to some of the world's leading service providers. For more information, please visit us at www.avici.com.