Hepatic fibrosis due to schistosomiasis japonica was examined by ultrasonography in a cross-sectional community study of 825 individuals on Jishan Island, Jiangxi Province, China. The prevalence of active infection was 39.4% with peak infection in the 10-19.9 years age group followed by a significant decline. A similar pattern was observed for intensity of infection. The prevalence of hepatomegaly in the midsternal line > or = 6 cm peaked at 60% in the fourth decade and remained elevated. A progressive increase in the severity of hepatic periportal fibrosis was observed with age, with advanced fibrosis peaking in the fifth decade. The proportion of individuals with advanced fibrosis was significantly greater in males than in females despite equivalent prevalence and intensity of schistosome infection. In addition, a positive association (P < 0.01) was found between periportal fibrosis and both hepatomegaly > or = 6 cm and splenomegaly. This study suggests that the natural history of schistosomiasis japonica in this hyperendemic community in China is marked by persistence of hepatomegaly and schistosome-induced periportal fibrosis in adults despite a decrease in the prevalence of infection.