Moscow, Russian Federation – Mobile TeleSystems OJSC (“MTS” – NYSE: MBT), the leading telecommunications provider in Russia and the CIS, announces that it will be changing its current American Depositary Receipt (ADR) ratio effective May 3, 2010.

The ratio will change from the current 1 ADR per 5 common shares to 1 ADR per 2 common shares. Existing ADRs will continue to be valid and will not have to be exchanged for new ADRs. The number of underlying common shares will remain unchanged.

To implement the change, MTS ADR holders of record at the close of business on April 28, 2010, will receive 1.5 ADRs for each ADR held. Additional ADRs are expected to be distributed on or around April 30, 2010, the ADR payment date.

Commenting on the ADR ratio change, Mikhail Shamolin, President and CEO of MTS, said: “MTS’ ADR price has increased more than 60% since the Company’s last effective stock split in January 2005. Changing the ADR ratio will bring the price more in line with our peer companies and support liquidity. We feel this will allow our ADRs to appeal to a broader investor base and provide additional flexibility to current shareholders in managing their portfolios.”