BACKGROUND: Toxic oxygen free radicals have been implicated as important pathologic mediators in many clinical disorders. Enhancing the intracellular content of antioxidant enzymes(superoxide dismutase, glutathione peroxidase, and catalase) can provide means of limiting biological damage caused by oxygen free radicals. The oxygen free radicals and changes of antioxidant enzymes are though to play a role in the pathogenesis of chronic obstructive pulmonary disease. METHOD: To investigate the pulmonary oxygen radical injury and the protective role of antioxidant enzymes in Chronic obstructive pulmonary disease(COPD), author measured the amount of thiobarbituric acid reactants, the activities of antioxidant enzymes and the sulfhydryl groups of glutathione in serum and red blood cells from the patients with COPD(COPD patients) and the normal controls. RESULTS: The thiobarbituric acid reactant in serum and .Ted blood cells of COPD patients was increased than those of the normal controls, and the superoxide dismutase activity in red blood cells was no statistical difference in both groups. But the glutathione peroxidase and catalase activities in red blood cells of COPD patients were significantly lowered than those of the normal controls. The sulfhydryl groups in seam and red blood cells were no statistically difference in both groups. CONCLUSION: These results suggest that the increased thiobarbituric acid reactants in serum and RBCs of chronic obstructive pulmonary disease mean oxygen radical toxicity, and the decreased glutathione peroxidase and catalase activities in RBC could take part in pathogenesis of chronic obstructive pulmonary disease.