We have examined the effects of inhalation anaesthetics on indocyanine green (ICG) clearance, as an index of hepatic function, in patients undergoing elective surgery. Recently, a new method has been developed to measure in real-time the disappearance rate of ICG from plasma. This method eliminates the multiple sampling and delay of the conventional ICG test. ICG clearance is displayed as two indices: K (ICG disappearance rate) and R(15) (ICG retention rate 15 min after injection of ICG 0.5 mg kg(-1)). This measurement was performed in patients before and after 1 MAC of sevoflurane (n = 6), 2 MAC of sevoflurane (n = 6), 1 MAC of isoflurane (n = 6), 2 MAC of isoflurane (n = 6), 1 MAC of halothane (n = 6) or 2 MAC of halothane (n = 6) without surgical stress. Although mean arterial pressure decreased significantly at 1 and 2 MAC of sevoflurane, 2 MAC of halothane, and 1 and 2 MAC of isoflurane, ICG clearance was maintained at awake levels, except at 2 MAC of halothane (K = mean-33 (SEM 3)%, R(15) = +90 (3)% from awake values). We conclude that sevoflurane and isoflurane have a more favourable effect on liver circulation than halothane.