

	China Mobile, World's Largest Wireless Service Provider, Chooses iBasis for International Internet Telephony Service China Mobile, Serving the World's Fastest Growing Wireless Market and Over 46 Million Mobile Users to Route International Voice and Fax Traffic Over the iBasis Network BURLINGTON, Mass., June 12, 2000 - iBasis Inc., (Nasdaq: IBAS), the leader in advanced Internet-based communications, today announced that China Mobile Telecommunications Corporation (China Mobile), the world's largest and fastest growing wireless carrier, has chosen the iBasis Network™ for global Internet Telephony. Under the terms of the agreement, China Mobile will be able to route international voice and fax traffic from its over 46 million customers over the global iBasis Network™. In addition, iBasis will be able to terminate its international traffic onto China Mobile's extensive network. "As one of the world's fastest-growing communications providers, we must continue to enhance international services for our customers," said Zhang Ligui, Head of the Preparatory Group of China Mobile. "We will take advantage of the opportunity to take part in the competition in the national and international markets, search for potential opportunities for profit and develop new services." "With China's Ministry of Information Industry predicting that the number of domestic mobile phone users is expected to reach 160 million in 2005, China clearly represents one of the fastest growing wireless markets in the world," said Ofer Gneezy, president and CEO of iBasis. "iBasis is pleased to be chosen by China Mobile as their international service provider. Our relationship with China Mobile further extends our already significant footprint in China and is further evidence that iBasis is able to meet the demands of the world's largest and fastest-growing carriers." The iBasis Network The iBasis Network is the world's largest international Cisco Powered Network (CPN) for Internet telephony. iBasis is the only Internet telephony carrier that guarantees service quality by offering the industry's first Service Level Agreement (SLA) for VoIP (Voice-over-Internet-Protocol). The key to maintaining the high level of quality required by the world's largest carriers is the company's proven, proprietary Assured Quality Routing™ (AQR™) technology. At the company's 24 x 7 Network Operations Center (NOC), the nerve center of The iBasis Network, located at iBasis' global headquarters in Burlington, Massachusetts, USA, engineers continuously monitor the global circuit-switched (PSTN) and packet-switched (IP) networks to ensure the highest quality of service to customers worldwide. iBasis has a long-standing strategic relationship with Cisco, as an alliance partner, an ecosystem partner, and one of only 21 Cisco service provider global accounts. About China Mobile Telecommunications Corporation China Mobile is the largest and fastest growing wireless carrier in China. In 1999, China Mobile successfully separated from China's leading domestic and international carrier, China Telecommunications Group Ltd (China Telecom). China Mobile ranks among China's largest state-owned companies, with annual revenues of $6.2 billion. With over 46 million customers, China Mobile's reach extends across all China's cities and 96 of its counties, with roaming services offered to a total of 56 countries and 95 cellular operators across all five continents. China Mobile offers such value-added services as fax and data, voicemail, calling number display, call transfer, call waiting, call barring, pre-paid cards, mobile phone banking, and mobile Internet. China Mobile has wholly-owned subsidiaries in 25 provinces. China Telecom (Hong Kong) Co. Ltd. is China Mobile's holding company and is valued at $100 billion US. China Mobile can be found on the Internet at http://www.chinamobile.com/english/index.html About iBasis Founded in 1996, iBasis (Nasdaq: IBAS) is the leader in advanced Internet-based communications. iBasis has built the world's first global IP network that delivers toll quality voice and fax service and other advanced hosted communications solutions, including OneCore VoCore, to global tier one carriers and other service providers. The iBasis Network is the world's largest international Cisco Powered Network for Internet telephony. More than 70 international carriers are iBasis customers, including 11 of the top 12 US international carriers. The company can be reached at its worldwide headquarters in Burlington, Mass., USA at 781-505-7500 or on the Internet at www.ibasis.net. Except for historical information, all of the expectations, projections and assumptions contained in the foregoing press release constitute forward-looking statements under the Private Securities Litigation Reform Act of 1995 and involve risks and uncertainties. Important factors that could cause actual results to differ materially from such forward-looking statements include, but are not limited to, the considerations described as "Risk Factors" in iBasis' prospectus dated March 9, 2000, and the company's other filings. Assured Quality Routing is a registered trademark, iBasis and The iBasis Network are trademarks and OneCore is a service mark of iBasis, Inc. Cisco and Cisco Powered Network are registered trademarks of Cisco Systems, Inc.