en تخصصي Special مروری Review Abstract Diabetes mellitus is one of the major metabolic disorders. Diabetes is recognized for severe complications including diabetic nephropathy, neuropathy and retinopathy. Long-lasting effect of hyperglycemia results in increased oxidative stress. Oxidative stress results from an imbalance between radical-generating and radical scavenging systems. Increased oxidative stress has been shown to be increased in both insulin-dependent (IDDM), and noninsulin-dependent (NIDDM) diabetes mellitus and it could cause initial β cell damage in type I diabetes, or impaired insulin production, release or function in type II diabetes. Therefore, people with diabetes may also have greater antioxidant requirements because of increased production of free radicals in hyperglycemia. In this article, oxidative stress, free radicals, antioxidants and various mechanisms of reactive oxygen species (ROS) formation such as polyol pathway, protein oxidation, advanced glycation endproducts and lipid peroxidation in diabetic patients will be surveyed. Diabetes, Lipid Peroxidation, Antioxidant, Oxidative Stress 40 45 http://ijdo.ssu.ac.ir/browse.php?a_code=A-10-30-43&slc_lang=en&sid=1 Robab Sheikhpour Yes Department Of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran