Abstract: The SOD- 1 contents in the serum of 106 cases with cerebral thrombosis and 34 cases with cerebral hemorrhage were determined with RIA. The results showed that all contents decreased and had nothing to do with the course of disease. These suggest that the cerebrovascular diseaes have the same pathologic effect of free radical injury and lipid peroxidation though their nature is different. Thus the supplied exogenous SOD and free radical scavenge will lighten the cerebral injury. The contents of SOD- 1 in serum in different courses have no difference. It suggests there existed the abnormallty of free radical metabolism, and those with dangerous factors and takin anti-free radical drugs in long term can protect recurrence.