Background & objectives: Smoking induces slow respiratory problems including chronic obstructive pulmonary disease (COPD). Cigarette smoke contains free radicals and decreases alphal antitrypsin levels in the body. The aim of the present study was to study the relationship between levels of α<inf>1</inf> antitrypsin and antioxidant status in smokers with COPD. Methods: A 20 controls without smoking and a total of 80 COPD cases with history of smoking were studied by spirometry and classified in to four groups according to GOLD. The α<inf>1</inf> antitrypsin, superoxide dismutase, vitamin E and vitamin C were measured in all the subjects respectively. Results:Controls had a normal spirometry. Cases showed a decrease in FEV1% with corresponding increase in the number of cigarettes/day. The α<inf>1</inf> antitrypsin, superoxide dismutase, vitamin E and vitamin C were decreased proportionately with increase in the number of cigarettes/day in cases when compared to the controls respectively. The difference in the means of each parameter between different case groups and controls is statistically highly significant. Interpretation & conclusion:Smoking inhibits α<inf>1</inf> antitrypsin. Cigarette smoke contains free radicals. The soot attracts neutrophils to the site of which releases more free radicals. Thus there is more elastase and less protease inhibitor, leading to lung damage. Our study showed decreased α<inf>1</inf> antitrypsin and antioxidant levels in smokers due to the increased inhibitory and consumption of antioxidants in the body due to increased production of free radicals respectively. © 2011 Elsevier B.V., All rights reserved.