The Convention on Psychotropic Substances of 1971 is a United Nations treaty designed to control psychoactive drugs such as amphetamine-type stimulants, barbiturates, benzodiazepines, and psychedelics signed in Vienna, Austria on 21 February 1971. The Single Convention on Narcotic Drugs of 1961 could not ban the many newly discovered psychotropics, since its scope was limited to drugs with cannabis, coca, and opium-like effects.