GlaxoSmithKline plc (GSK) is a British multinational pharmaceutical, biologics, vaccines and consumer healthcare company headquartered in London, United Kingdom. It is the world's fourth-largest pharmaceutical company measured by 2009 prescription drugsales (after Pfizer, Novartis, and Sanofi). It was established in 2000 by the merger of Glaxo Wellcome plc (formed from the acquisition of Wellcome plc by Glaxo plc) and SmithKline Beecham plc (formed from the merger of Beecham plc and SmithKline Beckman Corporation, which was formed by combining the Smith Kline French and Beckman companies). - Source: Wikipedia