We previously reported ultrasonographic and serologic abnormalities in 102 patients infected with Schistosoma japonicum in Leyte, The Philippines. These patients were subsequently treated with praziquantel (3 x 20 mg/kg), and changes in ultrasonographic images and the serum levels of liver function markers in 52 patients were followed up every three months for a period of 17 months. Improvement in the thickening of the portal vein wall and the intensity of echogenic bands was detected six months after treatment with praziquantel. The level of splenomegaly was also reduced in 42 patients who originally did not show the production of collateral vessels. A significant decrease in the serum total bile acid (TBA) level was detected in all patients six months after treatment with praziquantel. However, significant ultrasonographic changes could not be detected in the patients classified as type 3, with severe hepatic fibrosis caused by the long-term infection. These results clearly show that ultrasonographic examination, along with data on the serum TBA level, provides a sensitive tool to monitor the severity of hepatic fibrosis and portal hypertension caused by S. japonicum infection, as well as the improvement resulting from praziquantel treatment.