A field study in an area of intense infection with Schistosoma haematobium showed a 6-6% prevalence of bacteriuria in males under 25 which was significantly greater than in a non-endemic area where no cases were found. In older subjects the prevalence in both areas was less than 1%. Similarly designed studies showed a slight increase in mean blood pressure levels and in the prevalence of hypertension in the endemic area. This could not with certainty be attributed to the effects of S. haematobium and the levels recorded were unlikely to be associated with a poor prognosis. The findings suggest that bacteriuria but not hypertension, may sometimes determine the outcome of S. haematobium infection in this community.