BACKGROUND Chronic Obstructive Pulmonary Disease (COPD) is one of the leading causes of chronic morbidity and mortality. Apart from tobacco smoke, biomass fuel has been implicated as an important etiological factor for development of COPD. Oxidantantioxidant imbalance is known to play a key role in pathophysiology of COPD. The study was undertaken to evaluate the role of oxidative stress and antioxidant status among COPD cases due to tobacco smoking and biomass exposure. METHODS Serum MDA, and erythrocyte SOD and GSH levels, were estimated among 40 COPD cases due to tobacco smoking (Group 1), 20 COPD cases due to biomass exposure (Group 2). 40 age and sex matched healthy controls (Group 0) were also included. Serum MDA, SOD and GSH were measured calorimetrically by TBA method, Marklund & Marklund method and method by Beutler et al respectively. RESULTS IBM SPSS Ver. 20 was used for statistical analysis and preparation of tables. Significantly higher levels of MDA were seen among COPD cases due to tobacco smoke (58.08±52 vs 15.3705±6.6; p value <0.01) compared to controls. SOD levels were significantly lower in both case groups compared to controls (1123.3±301.2, 1147.01±200.5 vs 1315.23±209.1; p value<0.01). GSH levels were lower in tobacco smoking group when compared to biomass exposed group (7.98±2.7 vs 9.61±2.1; p value 0.01). Positive correlation was found between FEV1% and SOD in group 1 cases. CONCLUSIONS The results support the hypothesis of presence of increased oxidative stress and oxidant-antioxidant imbalance in pathogenesis of COPD. It plays an important role in disease severity which is higher among COPD in tobacco smokers compared to biomass exposed COPD.