The activity of antioxidative enzymes Cu, Zn-superoxidedismutase (SOD) and catalase as well as content of glutathione and activity of its metabolism enzymes--glutathione reductase (GR) and glutathione peroxidase (GP) were studied in red blood cells of 82 patients: with chronic obstructive pulmonary diseases (COPD, n = 26), chest osteomyelitis (n = 12), malignant (n = 21) and benign (n = 23) pulmonary lesions. Red blood cells from 26 donors served as a control. Enzymes of glutathione and catalase metabolism in the red cells inhibited their activity in all the above pulmonary diseases vs those of the controls: GR activity in COPD and chest osteomyelitis decreased by 40% and more, lung tumors--by 32-36%. GP activity--by 24-27%, 14-19%, respectively. Catalase activity in pulmonary diseases was suppressed by 38-45%. SOD activity in chest osteomyelitis and pulmonary tumors is lower by 37-40% while in COPD is higher by 36%. Activation of SOD in red cells in COPD may be regarded as a compensatory-adaptive response to excessive accumulation of free oxygen radicals in alveoli in COPD.