The effect of ginsenoside-Rd in ischemic-reperfused rats was examined. In control rats, blood and renal parameters and the activities of antioxidative enzymes in renal tissue deviated from the normal range, indicating dysfunction of the kidneys. In contrast, when ginsenoside-Rd was given orally for 30 consecutive days prior to ischemia and reperfusion, the activities of the antioxidation enzymes superoxide dismutase, catalase and glutathione peroxidase were higher, while malondialdehyde levels in serum and renal tissue were lower in the treated rats than in the controls. Decreased levels of urea nitrogen and creatinine in serum demonstrated a protective action against the renal dysfunction caused by ischemia and recirculation. On the other hand, it was demonstrated that ginsenoside-Rd affected cultured proximal tubule cells subjected to hypoxia-reoxygenation, probably by preventing oxygen free radicals from attacking the cell membranes.