The amount and distribution of tumor necrosis factor-alpha (TNF-alpha) in liver at various stages of Schistosomiasis japonicum-infected mice were immunohistochemically determined by SABC method. The results showed that the amount of TNF-alpha in liver began to increase at the 8th-12th week after infection, and reached a peak (9 mice reached 2+ grade or higher) 16 weeks after infection, which was higher than the levels 8 weeks after infection (P = 0.001) and was mainly scattered in and around egg granuloma. At the chronic stage of the infection, the amount of TNF-alpha in liver decrease not increase with an increased secretion of collagen in liver and development of hepatic fibrosis. On the contrary, FN, LN, type I and III collagen in liver began to rise 8-12 weeks after infection, and were linearly scattered around egg granuloma, reaching a peak (more than 70% of infected mice reached 3+(-)4+ grade) at the 20th and 24th week and they became wide, thick and retiform, and deposited around and in egg granuloma. After administration of recombinant TNF-alpha to the infected mice, the amount of FN and LN, the size and the inflammatory response of granuloma in liver showed no significant changes as compared with the untreated group at the same stage. However, the amount of type I collagen in liver increased, among which the amount of type I collagen was significantly higher than that in the untreated group at the same stage (P = 0.01), while similar changes were not observed when recombinant TNF-alpha was administrated to the healthy mice. It is suggested that TNF may play a role in stimulation of fibroblast in liver to proliferate and secrete collagen, but may need to cooperate with some factors.