iBasis Completes Redemption of Original Convertible Bond

All Remaining Long-Term Debt is Convertible by Holders at $1.85

BURLINGTON, MA— March 15, 2005 — iBasis, Inc. (OTCBB: IBAS), ), a leader in international long distance, VoIP, and prepaid calling cards, today announced that the company has redeemed the last of its original 5¾ percent Convertible Subordinated Notes due March 2005, which were issued in March 2000. Consistent with guidance the company issued on February 2, 2004, the company paid $895,000 plus accrued interest to satisfy 100% of the remaining outstanding notes. All of iBasis' outstanding bond debt is now convertible by holders at $1.85 per share.

"Five years ago we embarked on a massive and revolutionary endeavor to build a worldwide VoIP network," said Ofer Gneezy, president and CEO of iBasis. "To fund that activity we raised $150 million in equity and $150 million in convertible bond debt. We built a very advanced global network that now spans more than 100 countries, and we rapidly became one of the world's largest traders of international voice traffic. However, despite our continued explosive growth, the decline of the capital markets in the aftermath of the 'dotcom bubble' cut off access to continued funding, and the debt became an enormous burden for iBasis.

"This redemption today is symbolically important for us as it is the last of our original convertible notes. With all of our remaining long-term debt convertible and currently 'in the money', we are closer to becoming debt free."

Since the original debt offering in 2000, iBasis has grown its revenue from $61 million in 2000 to $264 million in 2004. The volume of traffic carried over the iBasis global VoIP network has grown from 600 million minutes in 2000 to approximately 5 billion minutes in 2004, which is more than 16% of the international VoIP market, according to projections from Telegeography.

Over the past three years, through a series of transactions, iBasis has reduced its debt from $210 million to $65 million.

About iBasis

Founded in 1996, iBasis (OTCBB: IBAS) is a leading wholesale carrier of international long distance telephone calls and a provider of retail prepaid calling services, including the Pingo™ web-based offering and disposable calling cards, which are sold through major distributors and available at retail stores throughout the U.S. iBasis customers include many of the largest telecommunications carriers in the world, including AT&T, Cable & Wireless, China Mobile, China Unicom, MCI, Sprint, Skype, Telefonica, Telenor, and Telstra. iBasis has carried more than 13 billion minutes of international voice over IP (VoIP) traffic over its global Cisco Powered™ network, and is one of the ten largest carriers of international voice traffic in the world¹. For three consecutive years service providers named iBasis the best international wholesale carrier in ATLANTIC-ACM's annual International Wholesale Carrier Report Card². iBasis was also ranked among the fastest-growing technology companies in New England in the 2002, 2003, and 2004 Technology Fast 50 programs 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.

Assured Quality Routing, ConnectPoint, and iBasis are registered marks, Pingo, DirectVoIP, The iBasis Network, Internet Central Office, Internet Branch Office, and IP CallCard are trademarks of iBasis, Inc. Cisco and Cisco Powered are registered trademarks of Cisco Systems, Inc. All other trademarks are the property of their respective owners.