The herbicide, paraquat, has caused numerous poisonings in man and farm animals since its interoduction. Althought the lungs are the primary sites of toxicological effect, other organs are also damaged, such as liver, heart, and kidney. The biochemical mechanisms responsible for the toxicity of the herbicide are not clearly understood. The purpose of the present study was to determine the hepatotoxity of paraquat in rats and the effects of glycyrrhizin on the paraquat toxicity. The experimental results are the followings. 1. The values of serum AST, ALT, LDH, ALP, glucose, and cholesterol were significantly increased in the paraquat administered group. 2. The TBA values in serum and liver were also increased in the treated group. 3. The biochemical parameters of serum, such as AST, ALT, LDH and TBA values, were significantly low in the paraquat plus glycyrrhizin group in comparison with that of the paraquat only. The above results suggest that the glycyrrhizin, somehow, detoxify the hepa to toxicity of paraquat in the experimenta-animals.