Infection with both urinary and intestinal schistosomiasis is prevalent with patchy distribution in Taiz Province, southwest Yemen Arab Republic. Schistosoma haematobium with a prevalence as high as 90% was found in the western, southern, and northern parts of the province. Among school children the overall prevalence was 37%. Infection rates did not differ significantly among various age and sex groups. Three species of Bulinus--B. beccarii, B. truncatus, and B. wrighti--have been found in the province, B. beccarii having the widest distribution and highest density. S. mansoni was found in most parts of the province. A 100% prevalence was found in some schools. The overall prevalence was 64% among school children and 68% among inhabitants of villages surveyed. Highest prevalence was found in the age group 10-20 years. Hepatosplenomegaly was prevalent among children in highly endemic areas. Biomphalaria pfeifferi, the intermediate host of S. mansoni, was found in most valleys.