A cross sectional survey for Schistosoma haematobium infections was undertaken in 12 primary schools in the city of Dar es Salaam. The prevalence in the schools ranged from 5.3 to 55.1%, with an overall prevalence of 19.3%. More males (23.5%) than females (15.0%) were infected, and the highest prevalence was recorded in the 11-16 year age group. Intensity of infection was high, ranging from 12 to 96 eggs/10 ml urine in individual schools. 26% of the infected excreted more than 50 eggs/10 ml urine, and high rates of haematuria and proteinuria were observed in infected children. Interviews indicated that the majority of the children had acquired their infection in the city. Malacological surveys showed two potential vectors, Bulinus (Physopsis) globosus and B. (Ph.) nasutus, to be common in Dar es Salaam. Laboratory and field findings confirmed that these two species were vectors of S. haematobium. Factors responsible for continued transmission in this urban environment are discussed.