Forty-six school children with japonicum schistosomiasis living in a village at Napu Valley, Indonesia were treated with praziquantel at a dosage of 70 mg/kg in two divided doses in a day. The number of children with palpable liver dropped significantly from 95.6% before treatment to 58.7% after treatment. The size of the liver was reduced in the majority of cases with a virtual disappearance of cases with very large liver (10 cm). Post-treatment increase of the liver size was observed in all 8 cases with small pre-treatment livers (0.5-1 cm). In contrast to the changes of the size of the liver after treatment, the number of children with palpable spleens before and after treatment was not significantly altered.