The present study evaluated the effect of glycyrrhizin (GR) on an injury of the liver caused by ischemia-reperfusion in rats. In the liver ischemia-reperfusion model, levels of serum GOT, GPT and LDH activities and lipid peroxides in the liver tissue were significantly increased. On the contrary, total glutathione content in the liver tissue and NADPH cytochrome P-450 reductase activity of liver microsomes were decreased. Pretreatment with GR 20 mg/kg, i.v. 10 min before induction of ischemia resulted in significant decreases in serum GOT, GPT, LDH activities and the lipid peroxide level and a higher tissue glutathione content during the period of reperfusion. Electron microscopic studies revealed various hepatocellular damages with an almost intact sinusoidal endothelium in ischemia-reperfused livers. However, the degree of damage was less severe in the livers from the rats pretreated with 20 mg/kg GR. The results indicate that GR is able to provide partial protection against ischemia-reperfused damage.