Dietary deficiency of antioxidants exacerbates ischemic injury in the rat kidney. We examined the effects of dietary deficiency of vitamin E and selenium on the ischemia-reperfusion model of renal injury in the rat. Deficient diets imposed for six weeks on three-week-old weanling rats led to no significant differences in body weights, serum creatinine, GFR, RBF, TmPAH or urinary total protein excretory rates prior to ischemia. Twenty-four hours after one hour of ischemia, animals on the deficient diet demonstrated more markedly impaired GFR, RBF, TmPAH and urine to plasma creatinine concentrations and an increased renal failure index. Tubular damage was more severe injury in the deficient animals. Lipid peroxidation, 15 minutes after the release of the ischemic clamp, was increased in the deficient animals. We confirmed the effects of our dietary manipulation in impairing the oxidant scavenging system in the deficient animals since glutathione peroxidase activity was reduced to less than 5% in the basal state, and this striking reduction persisted following ischemia. Plasma vitamin E concentrations were also markedly depressed in the deficient diets. This dietary deficiency also worsened the course of acute renal injury and was accompanied by 50% mortality compared to 0% mortality in the control animals. Thus, dietary deficiency of vitamin E and selenium led to greater structural and functional renal impairment and increased lipid peroxidation following ischemia. These data provide support for the role of reactive oxygen species in mediating ischemia-reperfusion injury. 