In Belo Horizonte, Minas Gerais, Brazil, the snail Biomphalaria straminea was found in the Pampulha region. Recently the snail was found in ditches in the old Santa Lúcia Reservoir, a now-extinct focus of schistosomiasis transmission by B. glabrata. The snails were collected and examined to verify whether they were naturally infected with Schistosoma mansoni. Negative specimens were used for breeding or infection with the LE strain of S. mansoni from the laboratory and another strain obtained from eggs found in the feces of a schoolchild (VGS) from Belo Horizonte. Among the 1890 snails collected from 1994 to 1995, none were infected with S. mansoni. Among 87 snails collected and exposed to the LE strain, 9 (10.3%) shed cercariae; among 83 snails from F1, and exposed to LE, 10 (12.0%) shed cercariae. Among 88 snails exposed to VGS, 10 (11.3%) shed cercariae. In Belo Horizonte, schistosomiasis is transmitted by B. glabrata and B. tenagophila. However, currently there exists the risk of appearance of a focus in which B. straminea could be the host if prophylactic measures are not taken by the authorities responsible for the construction of a park and lake at that site.