Transaction in Own Shares

GlaxoSmithKline PLC
23 March 2007



GlaxoSmithKline plc (the "Company") announces that in accordance with the
authority granted by shareholders at the Company's Annual General Meeting on 17
May 2006 it purchased 2,500,000 of its Ordinary shares of 25 pence each
("shares") on 23 March 2007 at a price of 1399.42 pence per share.

The Company intends to hold these shares in Treasury.

Following the purchase of these shares, the Company holds 269,082,678 of its
shares in Treasury.

The Company has 5,741,028,080 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 Transparency Directive's transitional
provision 6.












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