Cigarette smoking is a leading risk factor for coronary and vascular disease. Smokers are exposed to increased load of reactive oxidants which can promote peroxidation of lipids and lipoprotein resulting in increased arterial pressure. Therefore we intended to determine the ROS mediated endothelial dysfunction by assessing the extent of lipid peroxidation and to study the possible role of erythrocyte catalase activity and serum total bilirubin in smokers with and without hypertension. The study group included essential hypertensive smokers (n=22) and nonsmokers (n=22) and normotensive smokers (n=22) as cases and nonsmokers (n=22) as controls. Fasting blood sample were collected from both cases and controls. Eryth-rocyte catalase activity, serum total bilirubin, serum malondialdehyde (MDA) level were measured. ANOVA and Pearson’s correlation were used for statistical analysis. The present study showed significantly decreased erythrocyte catalase activity and serum total bilirubin was on the higher side of the physiological range. There was a significant rise in MDA levels in smokers with and without hypertension as compared to controls. The present study showed progressive increase in oxidative stress in smokers and hypertensives.