Abstract: A 7 years' follow-up observation on treatment of schistosomiasis with pyquiton was made in 1986. 339 cases were examined 1, 3, 6,12,30,48 and 84 months after treatment by stool hatching for miracidia and concentration method for eggs. The cumulative negative conversion rate was 99.2%. Detailed history was taken and physical examination was made in 224 out cf 339 cases. No sequelae were seen. Before treatment 93 cases (41.5%) had hepatomegaly below the costal margin, 166(69.6%) below the xyphoid process. 73 cases (32.6%) had splenomegaly. Follow-up examination 7 years post-treatment revealed hepatomegaly below the costal margin in 30 cases (14.4%), below the xyphoid process in 49 cases (21.9%) and splenomegaly in 18 cases(8%). Immunological tests performed 7 years post-treatment revealed a negative conversion rate of 91.7% (99/108) with ELISA and 85.2%(46/54) with COPT. The authors consider that pyquiton is the drug of choice for the treatment of schistosomiasis japonica.