Snail vectors of Schistosomiasis mansoni west of the San Francisco River, State of Bahia, were surveyed for the first time. In areas where the only vector found was Biomphalaria straminea, Schistosomiasis does not appear to be a medical problem. However, in areas where B. glabrata was collected, in addition t B. straminea, schistosomiasis was highly endemic. In spite of an abundance of surface water, no sanils were found in sparsely populated areas. This could change as a result of proposed schemes of new roads and irrigation systems. The results presented here have been combined with previously data in order to demonstrate a correia tion between the geografic distribuition of different species of snail vectors and the endemicity of schistosomiasis mansoni throughout Brazil.