The course of hepatosplenic schistosomiasis after mass chemotherapy with oxamniquine has been rarely reported. We report the effect of treatment in patients with advanced schistosomiasis mansoni living in area of Brazil highly endemic for this disease. A total of 739 inhabitants of a village were subjected to clinical and abdominal ultrasound examinations and were treated with oxamniquine. We have identified 84 individuals with hepatosplenic schistosomiasis. Alcohol abuse was associated with periportal thickening. Four years after treatment, 42 of the 84 individuals were re-examined and regression of splenomegaly was observed in 59% and of periportal thickening in 32%. Our data indicate that mass chemotherapy can lead to reduction of schistosomiasis morbidity but a significant group of patients (68%) will not improve. The association with alcohol abuse should be further evaluated. Thickening of the gallbladder wall can be a useful predictor of no involution of liver fibrosis after treatment.