Background : Isoflurane or propofol has been known to have a low potential for hepatotoxicity. The purpose of this study is to evaluate the effect of isoflurane or propofol on hepatic transaminase in healthy hepatitis B carrier patients. Methods : Forty-six patients who were healthy hepatitis B carriers were studied following an orthopedic surgery. The patients were randomly assigned to Group I (n = 22) who received isoflurane, or group P (n = 24) who received propofol. The plasma concentrations of aspartate aminotransferase (AST), and alanine aminotransferase (ALT) were measured on the day before the operation, and 1, 3, and 7 days after the operation. Results : The plasma concentrations of AST were not changed significantly until the 7th day post-operatively in both groups, and there were no significant differences between the two groups. The plasma concentrations of ALT were significantly decreased at 1 and 3 days postoperatively (P < 0.05) in both groups. However, it recovered to baseline concentrations at 7 days postoperatively. There were no significant differences between the two groups. Conclusions : The use of isoflurane or propofol does not increase the plasma concentrations of hepatic transaminase in Hepatitis B camer patients after an operation. (Korean J Anesthesiol 2000; 39: 662-666)