On the basis of Study, the following conclusions have been drawn: As the lung is exposed to high levels of oxygen, it is more susceptible to oxidants mediated injury.Gender based differences and socio-economic status are identifiable Risk Factors.Smoking is a major risk factor.Pulmonary functions are reduced in accordance with GOLD criteria.In mild COPD due to hyperinflation, FVC is increased as compared to healthy controls.The serum levels of MDA is lower in healthy subjects, as compared to COPD patients. In mild COPD group, the levels of antioxidant enzymes, Catalase and Superoxide Dismutase are elevated, as compared to healthy subjects due to an increase in the antioxidant activity in body in response to the mild oxidative stress.Greater the severity of the disease, higher will be the generation of the free radicals. Levels of antioxidants enzymes SOD, Catalase, GPX decreases from mild to very severe COPD groups. Oxidative stress plays a role in the patho-physiology of COPD.