A prospective study of the effect of schistosomiasis on the productivity of canecutters was carried out in northeastern Brazil during the harvest season 1977-1978. This study revealed that field workers bearing the hepatosplenic form of the disease produce significantly less in terms of cane tons cut than their pairs (intestinal form, used as controls). Futhermore, the productivity is gradually reduced the period of the sugar-cane cut season. Two workers (cases) with the hepatosplenic form had to leave field work during the experiment due to visible deterioration of their general health.