The effects of controlled hypotension induced with trimethaphan (TMP), nitroglycerin (TNG) or prostaglandin E1 (PGE1) during sevoflurane anaesthesia on hepatic function were studied in 28 patients undergoing spinal fusion surgery. Patients were randomly divided into three groups to receive TMP (group A, n=10), TNG (group B, n=10) or PGE1 (group C, n=8). Anaesthesia was maintained with N2O and sevoflurane. The mean arterial blood pressure was maintained at 60 mmHg for 90 min. Measurements included arterial ketone body ratio (AKBR-acetoacetate/3-hydroxybutyrate), SGOT, SGPT, LDH, blood glucose and blood gases were made. Measurements were taken before hypotension, 60 min and 90 min after starting hypotension, 60 min after recovery from hypotension and on the post-operative day. AKBR showed no significant change. SGOT, SGPT and LDH were within normal limits. Controlled hypotension induced with TMP, TNG or PGE1 under sevoflurane anaesthesia in surgical patients did not cause hepatocellular damage.