Since it's introduction in 1956 as a general anesthetic agent, halothane has enjoyed worldwide acceptance as a relatively safe and useful inhalational anesthetic. It is described as a universal anesthetic agent by Johnstone, but the question of its potential hepatotoxicity has not been definitely established. At our hospital, the patient whose liver function was in normal limit and had no history of the hepatitis, jaundice, exposing to hepatotoxic drug or alcoholism, and have received general anesthesia with halothane for biliary surgery as first operation from June 1979 to August 1980 were studied to evaluate the change of the liver function before and after kalothane anesthesia. The results were as follows; 1) In two cases, the liver funtion test showed the evidence of the hepatic damage. 2) The change of SGOT and bilirubin was statistically significant, but there wao no significant change of SGOT, alkaline phosphatase and T.T.T. 3) We thought that the changes of liver funtion test were due not only to halothane but also to the other factors. So, it may be good that repeated exposure to halothane is avoided.