Cercarial dermatitis is very common among rice farmers in the Caspian Sea area of Iran. The characteristic eggs of Orientobilharzia turkestanicum were found in the feces of a plowing bull. Fifty-six percent of uninfected Lymnaea gedrosiana maintained at 24-25 degrees C produced cercariae, identical to those from natural infections, 21 days after exposure to the miracidia obtained from the feces of the bull. Cercariae of O. turkestanicum from naturally infected L. gedrosiana produced dermatitis on the arm of one of us.