Stroke is the leading cause of mortality and morbidity world wide, particularly in the eld-erly. Oxidative stress is an independent risk factor by inducing production of oxygen free radicals in ischemic stroke. Because a relationship may be hypothesized between paraox-anase (PON) and malondialdehyde(MDA),the aim of this study was to investigate the rela-tionship between PON and oxidative stress with ischemic stroke by evaluating MDA concen-trations as indexes of oxidative stress. Our study included 100 patients of ischemic stroke and 100 controls.MDA levels was high and antioxidant activity Of PON was low in patients with ischemic stroke as compared to controls. Our findings suggest the importance of assess-ing the markers of oxidative stress and antioxidant capacity of PON indicating the involve-ment of lipid peroxidation leading to ischemic stroke.