FORM 6-K

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Report of Foreign Issuer
May 20, 2008

Pursuant to Rule 13a-16 or 15d-16 of
the Securities Exchange Act of 1934

Commission file number:  333-12032

Mobile TeleSystems OJSC

(Exact name of Registrant as specified in its charter)

Russian Federation

(Jurisdiction of incorporation or organization)

4, Marksistskaya Street
Moscow 109147
Russian Federation

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F.

Form 20-F   x   Form 40-F   o

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes   o   No   x

Press Release

Mobile TeleSystems announces financial results for the first quarter ended March 31, 2008

Moscow, Russian Federation – Mobile TeleSystems OJSC (“MTS” - NYSE: MBT), today announced its unaudited consolidated US GAAP financial results for the three months ended March 31, 2008.

Key Financial Highlights of Q1 2008

·                  Consolidated revenues up 37% y-o-y to $2,379 million

·                  Consolidated OIBDA(1) up 30% to $1,176 million y-o-y with 49.4% OIBDA margin

·                  Consolidated net income up 36% y-o-y to $610 million

·                  Free cash-flow(2) generation of $632 million

Key Corporate and Industry Highlights

·                  Appointment of Mr. Andrei Dubovskov as the new head of MTS Ukraine

·                  MTS first Russian company named as BRANDZ™ Top 100 Most Powerful Brands by Millwood Brown and Financial Times

·                  Consolidation of remaining stake in the Omsk subsidiary

·                  Redemption of the $400 million Eurobond issued in 2003

·                  Announcement of recommended dividend payment for FY 2007 of $1.2 billion or $3.12 per ADR(3)

Leonid Melamed, President and Chief Executive Officer, highlighted, “We are pleased to deliver on our promise of profitable growth throughout the Group’s operations. In Russia, we are witnessing clear momentum as we continue to add subscribers and realize the benefits of increasing voice and data usage. In Ukraine, we see positive trends in usage growth and service adoption, while in our remaining CIS markets, we are building out our networks to bring mobile service deeper into the local populations. In all, we are confident that we can sustain this momentum to continue executing on our corporate strategy.”

(1) See Attachment A for definitions and reconciliation of OIBDA and OIBDA margin to their most directly comparable US GAAP financial measures.

(2) See Attachment B for reconciliation of free cash-flow to net cash provided by operating activity.

(3) According to the Russian Central Bank exchange rate of 23.7939 RUR/$ as of May 5, 2008.

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Financial Summary (unaudited)

Group Operating Review

Market Growth

Mobile penetration(4) in markets of operation was:

·                  Down from 119% to 116% in Russia;

·                  Down from 120% to 119% in Ukraine;

·                  Up from 22% to 25% in Uzbekistan;

·                  Up from 7% to 10% in Turkmenistan;

·                  Up from 58% to 60% in Armenia;

·                  Up from 73% to 75% in Belarus.

Subscriber Development

The Company added approximately 3.0 million new customers during the first quarter of 2008 on a consolidated basis that were all added organically. During the quarter MTS:

·                  Added 2.5 million subscribers in Russia;

·                  Churned 0.4 million in Ukraine;

·                  Added 0.8 million subscribers in Uzbekistan;

·                  Added 110 thousand subscribers in Turkmenistan;

·                  Added 34 thousand subscribers in Armenia.

Our Belarus operations added approximately 140 thousand subscribers during the quarter.

Since the end of the first quarter to April 30, 2008, MTS has organically added a further 0.74 million users, expanding its consolidated subscriber base to 85.68 million.

Key Subscriber Statistics

(4) The source for all market information based on the number of SIM cards in Russia and Ukraine in this press release is AC&M-Consulting.

(5) Staring from Q1 2008 MTS employs a six-month inactive churn policy in Uzbekistan

(6) MTS owns a 49% stake in Mobile TeleSystems LLC, a mobile operator in Belarus, which is not consolidated.

2

Market Share

MTS was able to maintain its leading position in the majority of its markets of operation during the first quarter:

·                  Increased from 33% to 36% in Russia;

·                  Decreased from 36% to 35% in Ukraine;

·                  Increased from 50% to 52% in Uzbekistan;

·                  Decreased from 88% to 85% in Turkmenistan;

·                  Decreased from 74% to 73% in Armenia.

In Belarus, the market share increased to 54% from 53%.

Customer Segmentation

Subscriptions to MTS’ pre-paid tariff plans accounted for 86% of gross additions in Russia and 94% in Ukraine in the first quarter. At the end of the quarter, 88% of MTS’ customers in Russia were signed up to pre-paid tariff plans. In Ukraine, the share of customers signed to pre-paid tariff plans remained at 92%.

Russia Highlights

Ukraine Highlights

(7)   Including intercompany of $0.4 mln.

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Uzbekistan Highlights

Turkmenistan Highlights(9)

Armenia Highlights

Group Financial Position

MTS’ expenditure on property, plant and equipment in the first quarter totaled approximately $282 million, of which $151 million was invested in Russia, $103 million in Ukraine, $11 million in Uzbekistan, $15 million in Turkmenistan and $2 million in Armenia.

MTS spent approximately $61 million on the purchase of intangible assets during the quarter of which $54 million was spent in Russia, $6 million in Ukraine and $1 million in Armenia.

4

As of March 31, 2008, MTS’ total debt(10) was at $3.1 billion, resulting in a ratio of total debt to LTM OIBDA(11) of 0.7 times. Net debt amounted to $2.5 billion at the end of the quarter and the net debt to LTM OIBDA of 0.6 times.

***

For further information, please contact:

Mobile TeleSystems, Moscow

Investor Relations

Tel: +7 495 223 2025

E-mail: ir@mts.ru

***

Mobile TeleSystems OJSC (“MTS”) is the largest mobile phone operator in Russia and the CIS. Together with its subsidiaries, the Company services over 85.68 million subscribers. The regions of Russia, as well as Armenia, Belarus, Turkmenistan, Ukraine, and Uzbekistan, in which MTS and its associates and subsidiaries are licensed to provide GSM services, have a total population of more than 230 million. Since June 2000, MTS’ Level 3 ADRs have been listed on the New York Stock Exchange (ticker symbol MBT). Additional information about MTS can be found on MTS’ website at www1.mtsgsm.com.

***

Some of the information in this press release may contain projections or other forward-looking statements regarding future events or the future financial performance of MTS, as defined in the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. You can identify forward looking statements by terms such as “expect,” “believe,” “anticipate,” “estimate,” “intend,” “will,” “could,” “may” or “might,” and the negative of such terms or other similar expressions.  We wish to caution you that these statements are only predictions and that actual events or results may differ materially. We do not intend to update these statements to reflect events and circumstances occurring after the date hereof or to reflect the occurrence of unanticipated events. We refer you to the documents MTS files from time to time with the U.S. Securities and Exchange Commission, specifically the Company’s most recent Form 20-F. These documents contain and identify important factors, including those contained in the section captioned “Risk Factors” that could cause the actual results to differ materially from those contained in our projections or forward-looking statements, including, among others, potential fluctuations in quarterly results, our competitive environment, dependence on new service development and tariff structures, rapid technological and market change, acquisition strategy, risks associated with telecommunications infrastructure, risks associated with operating in Russia and the CIS, volatility of stock price, financial risk management and future growth subject to risks.

(10)      Total debt is comprised of the current portion of debt, current capital lease obligations, long-term debt and long-term capital lease obligations; net debt is the difference between the total debt and cash and cash equivalents and short-term investments; see Attachment B for reconciliation of net debt to our consolidated balance sheet.

(11)      LTM OIBDA represents the last twelve months of rolling OIBDA. See Appendix B for reconciliations to our consolidated statements.

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Attachments to the First Quarter 2008
Earnings Press Release

Attachment A

Non-GAAP financial measures. This press release includes financial information prepared in accordance with accounting principles generally accepted in the United States of America, or US GAAP, as well as other financial measures referred to as non-GAAP. The non-GAAP financial measures should be considered in addition to, but not as a substitute for, the information prepared in accordance with US GAAP.

Operating Income Before Depreciation and Amortization (OIBDA) and OIBDA margin. OIBDA represents operating income before depreciation and amortization. OIBDA margin is defined as OIBDA as a percentage of our net revenues. Our OIBDA may not be similar to OIBDA measures of other companies; is not a measurement under accounting principles generally accepted in the United States and should be considered in addition to, but not as a substitute for, the information contained in our consolidated statement of operations. We believe that OIBDA provides useful information to investors because it is an indicator of the strength and performance of our ongoing business operations, including our ability to fund discretionary spending such as capital expenditures, acquisitions of mobile operators and other investments and our ability to incur and service debt. While depreciation and amortization are considered operating costs under generally accepted accounting principles, these expenses primarily represent the non-cash current period allocation of costs associated with long-lived assets acquired or constructed in prior periods. Our OIBDA calculation is commonly used as one of the bases for investors, analysts and credit rating agencies to evaluate and compare the periodic and future operating performance and value of companies within the wireless telecommunications industry. OIBDA can be reconciled to our consolidated statements of operations as follows:

(12) Including intercompany of $2.2 mln.

(13) Including intercompany of $0.4 mln.

6

OIBDA margin can be reconciled to our operating margin as follows:

***

7

Attachment B

Net debt represents total debt less cash and cash equivalents and short-term investments. Our net debt calculation is commonly used as one of the bases for investors, analysts and credit rating agencies to evaluate and compare our periodic and future liquidity within the wireless telecommunications industry. The non-GAAP financial measures should be considered in addition to, but not as a substitute for, the information prepared in accordance with US GAAP.

Net debt can be reconciled to our consolidated balance sheets as follows:

Last twelve month (LTM) OIBDA can be reconciled to our consolidated statements of operations as follows:

8

Free cash-flow can be reconciled to our consolidated statements of cash flow as follows:

***

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Attachment C

Definitions

Subscriber. We define a “subscriber” as an individual or organization whose account shows chargeable activity within sixty one days in the case of post-paid tariffs, or one hundred and eighty three days in the case of our pre-paid tariffs, or whose account does not have a negative balance for more than this period.

Average monthly service revenue per subscriber (ARPU). We calculate our ARPU by dividing our service revenues for a given period, including interconnect and guest roaming fees, by the average number of our subscribers during that period and dividing by the number of months in that period.

Average monthly minutes of usage per subscriber (MOU). MOU is calculated by dividing the total number of minutes of usage during a given period by the average number of our subscribers during the period and dividing by the number of months in that period.

Churn. We define our “churn” as the total number of subscribers who cease to be a subscriber as defined above during the period (whether involuntarily due to non-payment or voluntarily, at such subscriber’s request), expressed as a percentage of the average number of our subscribers during that period.

Subscriber acquisition cost (SAC). We define SAC as total sales and marketing expenses and handset subsidies for a given period. Sales and marketing expenses include advertising expenses and commissions to dealers. SAC per gross additional subscriber is calculated by dividing SAC during a given period by the total number of gross subscribers added by us during the period.

***

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MOBILE TELESYSTEMS

CONDENSED UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS

FOR THE THREE MONTHS ENDED MARCH 31, 2008 AND 2007

(Amounts in thousands of U.S. dollars, except share and per share amounts)

11

MOBILE TELESYSTEMS

CONDENSED UNAUDITED CONSOLIDATED BALANCE SHEETS

AS OF MARCH 31, 2008 AND DECEMBER 31, 2007

(Amounts in thousands of U.S. dollars, except share amounts)