GlaxoSmithKline. GlaxoSmithKline plc (GSK) is a British multinational pharmaceutical, biologics, vaccines and consumer healthcare company headquartered in London

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 drug sales (after Pfizer, Novartis, and Sanofi). It was established in 2000 by the merger of Glaxo Wellcome plc and SmithKline Beecham plc.

In 1880, Burroughs Wellcome & Company was founded in London by the American pharmacists Henry Wellcome and Silas Burroughs. Glaxo was founded in Bunnythorpe, New Zealand, in 1904. Originally Glaxo was a baby food manufacturer processing milk into a baby food of the same name: the product was sold under the slogan "Glaxo builds bonny babies" from 1908. Glaxo became Glaxo Laboratories, and opened new units in London in 1935. After the company bought Meyer Laboratories in 1978, it started to play an important role in the US market. Burroughs Wellcome and Glaxo merged in 1995 to form GlaxoWellcome. Three years later GlaxoWellcome bought Polfa Poznan Company in Poland.

In 1843, Thomas Beecham launched his Beecham's Pills laxative in England giving birth to the Beecham Group. By the 1960s, Beecham was extensively involved in pharmaceuticals.In 1830, John K. Smith opened its first pharmacy in Philadelphia. In 1865, Mahlon Kline joined the business which 10 years later became Smith, Kline & Co. In 1989 it merged with Beecham to form SmithKline Beecham plc. The headquarters of the company was moved to England. To expand research & development in the US, SmithKline Beecham bought a new research center in 1995.

Glaxo Wellcome and SmithKline Beecham merged on in December 2000, forming GlaxoSmithKline.

GSK has a portfolio of products for major disease areas including asthma, cancer, virus control, infections, mental health, diabetes and digestive conditions. It also has a large consumer healthcare division that produces and markets oral healthcare and nutritional products, drinks and over-the-counter medicines, including Sensodyne, Boost, Horlicks, Lucozade, Ribena and Gaviscon.

GSK has a primary listing on the London Stock Exchange and is a constituent of the FTSE 100 Index. As of 6 July 2012, it had a market capitalisation of £74.8 billion, the fifth-largest of any company listed on the London Stock Exchange. It has a secondary listing on the New York Stock Exchange.

GSK employs 97,000 people worldwide of whom about 12,500 work in research and development. Its global headquarters are GSK House in Brentford, United Kingdom, with its United States headquarters based in Research Triangle Park in North Carolina^[34] and its consumer products division based in the Pittsburgh suburb of Moon Township, Pennsylvania. The research and development division has major facilities in South East England, Philadelphia and Research Triangle Park in North Carolina. GSK has a presence in 99 cities across 39 countries.

GSK's single largest market is in the United States, which generates approximately 45 % of its revenues, although the company sells its products in around 70 countries.