iBasis Named Fastest Growing Technology Company in New England

Company Achieves #1 'Fast 50' Ranking While Focused on Increasing Margin, Reducing Cost and Strengthening Balance Sheet

BURLINGTON, MASS. - September 22, 2003 - iBasis, Inc. (OTCBB: IBAS), the leader in Internet-based voice communications, today announced that it received the #1 ranking among New England's fastest growing technology companies in Deloitte & Touche's prestigious "Technology Fast 50" Program for New England. The annual Technology Fast 50 program is a ranking of the 50 fastest growing technology companies in the area based on revenue growth over the five-year period from 1998-2002. "The #1 ranking is especially gratifying now as it comes after more than a year of intense focus on reducing costs, divesting of unproductive business units, strengthening our balance sheet, and increasing margins, sometimes at the expense of revenue growth," said Ofer Gneezy, president and CEO of iBasis. "Increasing scale while simultaneously improving profitability is a significant challenge. We expect that our recent addition of a retail prepaid service will contribute to both."

iBasis has received a #1 ranking from the Deloitte & Touche program for four consecutive years, including #1 "Rising Star" rankings in 2000 and 2001 and #1 Fast 50 rankings for 2001 and 2002. Winners of the 20 regional Technology Fast 50 programs in the United States and Canada are automatically entered in the Deloitte & Touche Technology Fast 500 program, which ranks North America's top 500 fastest growing technology companies. In 2002, iBasis was ranked #8 in the national Technology Fast 500 program. For more information on the Deloitte & Touche Fast 50 or Fast 500 programs, visit www.fast500.com.

About iBasis

Founded in 1996, iBasis (OTCBB: IBAS) is a leading provider of wholesale international telecommunications services. For the past two years the company has been named by service providers as the best international wholesale carrier in Atlantic-ACM's annual International Wholesale Carrier Report Card¹. iBasis is a preferred provider for many of the largest carriers in the world, including AT&T, Cable & Wireless, China Mobile, China Unicom, MCI, Sprint, Telefonica, Telenor, and Telstra. iBasis has carried more than six billion minutes of international voice traffic over its global Cisco Powered Network™, and is one of the ten largest carriers of international voice traffic in the world². In addition to its wholesale international telecommunications services, iBasis provides retail prepaid calling cards to major distributors, utilizing the international iBasis Network. Based on its revenue growth from 1997 through 2001, iBasis was ranked the #8 fastest-growing technology company in North America and the #1 fastest-growing technology company in New England in the Technology Fast 500 national program sponsored by Deloitte & Touche. The company can be reached at its worldwide headquarters in Burlington, Massachusetts, USA at 781-505-7500 or on the Internet at www.ibasis.com.

The New England Technology Fast 50 program is presented by Deloitte & Touche and Hale and Dorr, in association with the sponsor, Mazonson Inc. In addition, Mass High Tech and Trinity Communications are associated with the program.