Transaction in Own Shares

GlaxoSmithKline PLC
17 March 2008


GlaxoSmithKline plc (the 'Company') announces that in accordance with the
authority granted by shareholders at the Company's Annual General Meeting on 23
May 2007 it purchased 4,000,000 of its Ordinary shares of 25 pence each
('shares') on 17 March 2008 at a price of 1014.05 pence per share.


The shares will be cancelled.


Following the cancellation of these shares, the Company holds 504,194,158 of its
shares in Treasury, representing 9.25% of the total voting rights in the
Company.


The Company has 5,434,994,058 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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