The incidence of poliomyelitis throughout the world is outlined on the basis of official statistics-in many cases necessarily provisional or approximate-augmented by information from wider and unpublished sources. Available reports on the virus types responsible for poliomyelitis outbreaks in recent years are also summarized.A rise in apparent incidence occurred in the following countries in 1953: Africa-Angola, Egypt (largely due to improved reporting), Middle Congo (French Equatorial Africa), Morocco (French Zone), Ruanda-Urundi, Tanganyika, Tunisia, Union of South Africa, and Upper Volta (French West Africa); America-Argentina, Brazil, Canada, Colombia, El Salvador, Greenland, Mexico, Nicaragua, and Uruguay; Europe-Austria, Finland, France, Greece, Italy, Norway, Republic of Ireland, Saarland, Sweden, Switzerland, Trieste (British/United States Zone), Turkey, United Kingdom, and Yugoslavia. The epidemics in Canada and Sweden were the most severe ever recorded in the two countries. The incidence decreased markedly in: Africa-Kenya, Mauritius, Southern Rhodesia, and Uganda; America-Chile (probably), Cuba, and the USA; Asia-Cambodia, Ceylon, India, Israel, Lebanon, Philippines, and Thailand; Europe-Belgium, Denmark, Federal Republic of Germany, Luxembourg, the Netherlands, Portugal, and Spain; Oceania-Gilbert and Ellice Islands, Hawaii Islands, and New Zealand.While data on virus types are insufficient for any definitive conclusions to be reached as to responsibility for poliomyelitis outbreaks, it would appear that all three types are widely distributed, while in the selected areas where polioviruses have been typed, type 1 virus has been isolated the most frequently.