The Convention on the Prohibition of the Development, Production and Stockpiling of Bacteriological (biological) and Toxin Weapons and their destruction, better known as the BTWC or BWC, attained thirty years of existence on March 26, 2005. The BTWC, a multilateral treaty, was negotiated from 1969-1971. It was opened for signature in London, Moscow and Washington DC on April 10, 1972. It entered into force on March 26, 1975, with 43 member countries, after ratification by the three Depository States—the USA, the Soviet Union (erstwhile) and the United Kingdom.