Babesia cynicti originally was described from spleen smears of two yellow mongooses (Cynictis penicillata), the main vectors of rabies on the central plateau of South Africa. During a detailed study of the epizootiology of rabies in that area between October 1991 and February 1993, sets of blood smears from three yellow mongoose populations were available for examination. Babesia cynicti was found in 50 of 56 specimens from Rooiwal, north of Pretoria, in 13 of 18 specimens from near Ermelo in the southeastern Transvaal, and in 22 of 23 specimens from Potchefstroom in the western Transvaal.