Introduction: Oxidant-antioxidant imbalance plays a major role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Recently, most of the studies are concentrated on the evaluation of oxidant-antioxidant balance in exhaled breath condensate and in other body fluids in COPD patients. Aims and Objectives: In this study, we investigated oxidant-antioxidant balance in systemic circulation of patients with COPD. Serum malondiladehyde (MDA), protein carbonyl (PC) and whole blood reduced glutathione (GSH) levels were determined in 60 patients with stable COPD and it compared with 60 age and sex matched healthy controls. Materials and Methods: The levels of serum MDA, protein carbonyl and whole blood reduced glutathione were determined according to Buge and Aust method, Levin et al and Beutler et al method. Results: Serum MDA and PC levels were significantly increase in COPD patients as compared to healthy controls. We found significantly decreased levels of erythrocyte GSH in stable COPD patients as compared to healthy controls. Conclusion: Tobacco smoking cause increase in oxidative stress and reduction in antioxidant level in COPD patients. From these findings we conclude that there is disturb oxidant __ampersandsignndash; antioxidant balance in COPD patients and this imbalance is related to long term history of tobacco smoking.