Isoflurane and enflurane are currently used on orthognathic surgery in Korea. Since starting to use enflurane and isoflurane in orthognathic surgery, we have questioned their effect on liver function. Many studies have reported liver function after enflurane and isoflurane anesthesia. Although both enflurane and isoflurane are less hepatotoxic than halothane, some cases of liver dysfunction have been reported after enflurane and isoflurane anesthesia. And, we know that isoflurane is less hepatotoxic than its predecessors, enflurane. But, fulminant liver failure and necrosis were also reported after isoflurane anesthesia. The purpose of this study was to compare immediate liver function in healthy orthognathic surgical patients receiving enflurane or isoflurane anesthesia. To assess the effect of enflurane and isoflurane on liver function, we measured pre-and post-operative serum concentrations of aspartate aminotransferase(AST), and alanine aminotransferase(ALT), alkaline phosphatase(ALP), total bilirubin(Tbil).