Oxidative stress is known to involve in the pathogenesis of various disease including coronary artery disease (CAD). Diabetes mellitus and obesity are known to be the risk factors for CAD. Hence in the present study we investigated the levels of oxidative stress marker, Malondialdehyde (MDA) which is a breakdown product of peroxidation of long chain fatty acids in patients with diabetes mellitus or obesity to identify the possible link between oxidative stresses in the occurrence of CAD in diabetes mellitus or obesity. Blood samples were collected from patients with CAD, DM and obese subjects and analyzed for MDA estimation by HPLC. Results show that there was a significant increase in serum MDA levels with CAD, DM and obese subjects when compared to healthy controls. In conclusion, based on the result obtained it may be presumed that increased oxidative stress seen in diabetes mellitus and obese subjects is one of the risk factors for CAD.