Abstract: SOD activity levels in the peripheral blood cells of 19 cases of early schistosomia- sis, 43 cases of late schistosomiasis, 9 cases of late schistosomiasis who have been essentially cored and 30 cases of healthy persons wfere determined.The results showed that SOD activity is 98 3U in patients with early schisto-miasis, 486U in patients of late schistosomiasis, 617U in patients of late schistosomiasis who have been essentially cured, and 1,411U in healthy persons, respectively.There exists a significant difference between the SOD activity in normal healthy persons and in patients of late schistosomiasis (P0.001).