Earlier treaties had only controlled opium, coca, and derivatives such as morphine, heroin and cocaine. The Single Convention, adopted in 1961, consolidated those treaties and broadened their scope to include cannabis and drugs whose effects are similar to those of the drugs specified. The Commission on Narcotic Drugs and the World Health Organization were empowered to add, remove, and transfer drugs among the treaty's four schedules of controlled substances. The International Narcotics Control Board was put in charge of administering controls on drug production, international trade, and dispensation. The United Nations Office on Drugs and Crime (UNODC) was delegated the Board's day-to-day work of monitoring the situation in each country and working with national authorities to ensure compliance with the Single Convention. This treaty has since been supplemented by the Convention on Psychotropic Substances, which controls LSD, MDMA, and other psychoactive pharmaceuticals, and the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances, which strengthens provisions against money laundering and other drug-related offenses.

As of May 2013, the Single Convention has 184 state parties. The Holy See plus all members of the UN are state parties, with the exception of Afghanistan, Chad, East Timor, Equatorial Guinea, Kiribati, Nauru, Samoa, South Sudan, Tuvalu, and Vanuatu.