The expression of superoxide dismutases (SODs) has been shown to differ between lung tumor and tumorfreetissues. In the present study, we investigated the association between serum SOD activity and the risk oflung cancer mortality, based on a nested case-control design study within the Japan Collaborative Cohort Study,with a sample of 193 lung cancer patients and 573 matched controls. Blood samples were obtained at the baselineand stored at -80ºC until analysis for SOD levels. Serum levels of SODs were divided into quartiles, with the firstquartile used as the reference. A conditional logistic model was used to estimate odds ratios (ORs) for lungcancer mortality associated with serum SOD quartile levels. The adjusted ORs and 95% CIs for the second,third; and fourth SOD quartiles were 0.80 (95%CI: 0.49-1.29), 1.32 (0.78-2.25), and 1.07 (0.60-1.89), respectively.In analyses stratified by observation period, the adjusted ORs of the respective quartiles were 0.56 (95%CI:0.30-1.07), 1.16 ( 0.57-2.37), and 1.11 (0.52-2.35) for the period from the baseline to 1994; and the adjusted ORsof 1.36 (95%CI: 0.65-2.85), 1.71 (0.75-3.87), and 1.06 (0.44-2.53) for the period after 1994. To conclude, wefound no significant association between serum SOD level and the risk of deaths from lung cancer in the presentstudy.