GlaxoSmithKline plc (the 'Company') announces that in accordance with the authority granted by shareholders at the Company's Annual General Meeting on 21 May 2008 it purchased 850,000 of its Ordinary shares of 25 pence each ('shares') on 29 September 2008 at a price of 1,199.33 pence per share. 

The shares will be cancelled. 

Following the cancellation of these shares, the Company holds 474,194,158 

 of its shares in Treasury, representing 9.09% of the total voting rights in the Company. 

The Company has 5,217,945,776 shares in issue (excluding Treasury shares). This number represents the total voting rights in the Company and may be used by shareholders as the denominator for the calculations by which they can determine if they are required to notify their interest in, or a change to their interest in the Company under the Financial Services Authority's Disclosure and Transparency Rules. 

This announcement does not constitute, or form part of, an offer or any solicitation of an offer to purchase or subscribe for securities in any jurisdiction and is in conformity with the Financial Services Authority's Disclosure and Transparency Rules. 

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