Chronic exposure to supraphysiologic glucose concentrations causes functional damage to cells and tissues, a process known as glucose toxicity. Recent research indicates that one important mechanism for glucose toxicity is oxidative stress. Glucose has been shown to form reactive oxygen species through several metabolic pathways. The pancreatic islet is distinguished by its relatively low antioxidant enzyme content and activity, which render it especially susceptible to oxidative stress. Adenoviral overexpression of glutathione peroxidase as well as gamma-glutamylcysteine ligase have been shown to protect the islet against oxidative stress. Antioxidants have been shown to brake the worsening of diabetes by improving beta cell function in animal models. These observations suggest that enhancing antioxidant defense mechanisms in pancreatic islets may be a valuable pharmacologic approach to managing diabetes.