Following the diagnosis in 1981 of the first case of Crimean-Congo hemorrhagic fever (CCHF) in South Africa, an antibody survey was undertaken on cattle sera to determine the distribution of the virus and specific diagnostic tests were routinely applied to specimens from suspected cases of hemorrhagic fever to establish the medical significance of its presence. Antibody to CCHF virus was demonstrated by reversed passive hemagglutination-inhibition technique in 2,460/8,667 (28%) cattle sera and in 140/180 herds tested in South Africa, as well as in 347/763 (45%) cattle sera and in 32/34 (94%) herds tested in Zimbabwe. The antibody was found in all major cattle farming areas, but was of low prevalence along the southern coast where 2 of the 3 species of Hyalomma tick which occur in South Africa are absent. From February 1981 to January 1986, inclusive, 29 indigenous cases of CCHF were diagnosed in 16 outbreaks which arose in various locations throughout South Africa. A further 2 imported cases of CCHF arose in Zaire and Tanzania. The clinical features of infection conformed to the classical descriptions of CCHF in the Soviet Union. The fatal outcome in 11/31 cases indicates that the African disease is no less severe than that which occurs in Eurasia. It is inferred that the virus is widespread in all countries in Africa and Eurasia which lie within the limits of world distribution of ticks of the genus Hyalomma.