To assess the effect of sevoflurane anaesthesia on hepatocellular integrity, we measured plasma concentrations of glutathione S-transferase (GST) before anaesthesia and 1, 3, 6 and 24 h after the end of anaesthesia in 41 healthy, Japanese patients undergoing elective, body surface surgery. Sevoflurane (approximately 1.0 MAC) was delivered in 50-66% nitrous oxide in oxygen via a circle system, with a fresh gas flow of 6 litre min-1. Ventilation was spontaneous in all patients. Mean duration of anaesthesia was 101 min. Concentrations of GST increased significantly 1 h after the end of anaesthesia (P = 0.0075), but this was not significantly different from preoperative concentrations at 3, 6 and 24 h. Three patients developed a large secondary increase in GST concentrations at 24 h. The increase observed at 1 h was probably a result of reduced total liver blood flow; the mechanism for the secondary increase at 24 h is unclear but the possibility that products of sevoflurane biotransformation are responsible cannot be excluded.