The livers of impala (Aepyceros melampus) collected in the Mlawula-Mbuluzi-Simunye Nature Reserve and Protected Area complex in northeastern Swaziland from October 1985 to September 1986 were infected with three species of helminths: a nematode (Cooperioides hepaticae), a cestode (Stilesia hepatica), and a trematode (Fasciola gigantica). Cooperioides hepaticae caused a severe cholangitis. Lambs were infected at 1.5 to 2 mo of age, and the prevalence increased to 100% by 5 mo of age. The prevalence was 82% in yearlings and 44% in adults, with the highest prevalence and intensity of infection at the end of the dry season. Stilesia hepatica was found primarily in adults. Heavy infections caused a thickening and distension of the main bile ducts, but no changes were evident in the liver parenchyma. Fasciola gigantica, found only in one adult male, caused a thickening and distension of main bile duct. There was no apparent association between the helminth infections and body condition.