The function of spontaneous T suppressor cell (STs) of peripheral blood was detected in 17 patients with acute schistosomiasis japonica, 14 cases with chronic schistosomiasis and 25 patients with advanced schistosomiasis. The subset of T cell were simultaneously phenotyped in all cases except 10 patients with advanced schistosomiasis. Among the patients with acute schistosomiasis the rates of OKT3 + (pan T cell), OKT4+ (helper T cell) and OKT8 + (suppressor/cytotoxic T cell) were all significantly increased, and the function of STs was normal. In chronic and advanced schistosomiasis, the rate of OKT8 + T cell was raised, the rate of OKT3+ T cell and ratio of OKT4+/OKT8+ were statistically reduced, and the function of STs was significantly increased. The rate of OKT8+ T cell was negatively correlated with the function of STs in acute schistosomiasis, whereas in chronic and advanced rchistosomiasis, the rate of OKT8 + T cell had significant positive correlation with STs function while OKT4 +/OKT8 + had significant negative correlation with this function. The results indicate that the cellular immune response is increased in patients with acute schistosomiasis and down regulated in patients with chronic and advanced schistosomiasis. The function of T suppressor cell and the subset of T cell may play an important role in the immunoregulation of patients with schistosomiasis japonica.