Abstract: Manganese-containing superoxide dismutase （Mn-SOD） activities in lung cancer tissues from 5 patients with pulmonary carcinoma were measured by the nitrite formation method, lipid peroxide （LPO） values being measured bv spectrophometry of thiobarbituric acid reaction. The results obtained show that Mn-SOD activities exhibit most evidently in lung cancer tissues, less evidenatly in peripheral tissues around the lung cancer, but the least in normal peripheral lung tissues, indicating a declined tendency as definitely proved by statistical treatment （P＜0.01）. In addition, LPO values are found to be lower in lung cancer tissies than those in normal peripheral tissues.