Oxidative stress is believed to play an important role in the development of vascular complications associated with diabetes mellitus. We examined the antioxidative effect of sesamin and sesamolin on the preventing the development of insulin dependent diabetes mellitus using streptozotocin-induced Sprague Dawley diabetic rats. From 48 hours after injection of streptozotocin (60 mg/kg body weight), a portion of diabetic rats were fed with 0.2% sesamin and sesamolin containing diet for 3 weeks. There were significant differences of blood glucose and kidney weight between diabetic ports and control. Sesamin and sesamolin increased glutathione-S-transferase activity in kidney. The concentration of the thiobarbituric acid-reactive substances in the serum, liver, and kidney of diabetic rats administered sesamin and sesamolin decreased significantly as compared with that of the non-treated diabetic group. Dietary sesamin and sesamolin suppressed the oxidative stress in the diabetic rats. These results demonstrated that sesamin and sesamolin are potential and effective antioxidants that can protect the complications associated with diabetes.