Russia’s Mobile TeleSystems (MTS) Enlists iBasis Premium Voice Service for International Calling

iBasis Premium Voice Service Gives Russia’s Largest Mobile Operator High-Quality, Efficient Global Termination to Fixed and Mobile Networks

BURLINGTON, Mass. – 12/16/2009 – December 16, 2009 iBasis (NASDAQ: IBAS), a KPN affiliate, today announced that Mobile TeleSystems (MTS), Russias largest mobile operator, is now using iBasis Premium Voice service to complete international calls for its customers. By interconnecting with iBasis, MTS joins more than 1,000 carrier customers from all segments of telecom that use iBasis for all or part of their international voice service.

With iBasis Premium Voice, MTS gains very high quality worldwide voice termination through a single connection to the iBasis global network. The service guarantees transfer of Caller Line Identifier (CLI) to mobile and fixed destinations and provides support for international roaming worldwide.

With more than 96 million mobile customers and annual revenues in excess of $10 billion, MTS is a leading provider of mobile communications in Russia, Ukraine, Uzbekistan, Turkmenistan, Armenia and Belarus. This interconnect strengthens iBasis position in Russia, Eastern Europe and Central Asia, a rapidly growing region for mobile telecommunications services. The Russian market alone is the fourth largest mobile telecommunications market in the world with mobile service penetration exceeding 125% and annual growth rate still strong at 14.5 percent.(1)

“Russia, Eastern Europe and Central Asia are large, rapidly growing markets for mobile telecommunications services, and MTS has established itself as the leader within the region, said Ofer Gneezy, president and CEO of iBasis. Now, through iBasis Premium Voice, MTS can better serve customers and expand its market reach by offering an even higher quality international mobile calling service cost effectively.

“As the leading mobile operator in Russia and the surrounding region, our goal is to provide the most reliable, cost-efficient voice service possible and to continue to increase our market share, said Evgeny Moskalev, Fixed Line, Broadband, Roaming and Interconnect Director, Corporate Center of MTS. Our customers expect our services to perform at a high level of quality domestically and internationally. iBasis Premium Voice has enabled us to fulfill their expectations.

About iBasis
Founded in 1996, iBasis (NASDAQ: IBAS) is a leading wholesale carrier of international long distance telephone calls and a provider of retail prepaid calling services and enhanced services for mobile operators. iBasis customers include KPN, KPN Mobile, E-Plus, BASE, TDC and many other large telecommunications carriers such as Verizon, Vodafone, China Mobile, China Unicom, IDT, Qwest, Skype, Telecom Italia, and Telefonica. In October 2007, iBasis acquired KPN Global Carrier Services to create one of the three largest carriers of international voice traffic in the world (2), and KPN became a majority stockholder of iBasis. The company carried approximately 24 billion minutes of international voice traffic in 2008. The Company can be reached at its worldwide headquarters in Burlington, Mass., USA at +1 781-505-7500 or on the Internet at www.ibasis.com.

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1. Cellular-News, Russia’s Penetration Over 125% and No Sign of Stopping. 19 December 2008.http://www.cellular-news.com/story/35266.php

2. Based on Telegeography 2009 and iBasis and KPN Global Carrier Services 2008 traffic.

iBasis and KPN are registered marks. All other trademarks are the property of their respective owners.

Except for historical information, all of the expectations, plans and assumptions contained in the foregoing press release constitute forward-looking statements under Section 21E of the Securities Exchange Act of 1934 and involve risks and uncertainties that could cause results to vary materially. For a description of certain of these risks and uncertainties please read the Company’s most recent Annual Report on Form 10-K and other periodic and current reports, all of which are available atwww.sec.gov. Such forward-looking statements are only as of the date they are made.