The effects of proanthocyanidin-rich extract in rats subjected to renal ischemia-reperfusion were examined. Proanthocyanidin-rich extract, which is prepared from grape seeds (Vitis vinifera L.), was given orally at doses of 5 and 10 mg/kg body weight/d for 20 consecutive days prior to ischemia-reperfusion. Administration of proanthocyanidin-rich extract attenuated renal dysfunction, as indicated by serum urea nitrogen and creatinine levels. Additionally, in the ischemic-reperfused kidneys, increased levels of thiobarbituric acid (TBA)-reactive substance and alterations of antioxidant enzyme activities such as superoxide dismutase, catalase and glutathione peroxidase (GSH-Px) were observed. Proanthocyanidin-rich extract-treated groups showed significantly reduced renal TBA-reactive substance levels and enhanced catalase and GSH-Px activities. These results suggest that proanthocyanidin-rich extract has protective effects against ischemia-reperfusion-induced renal damage associated with oxidative stress.