Exacerbation of pre-existing liver disease after halothane anaesthesia has been reported in adult patients. A prospective study was performed in 38 children with biopsy-proven liver disease to assess the effect of surgery and halothane anaesthesia on liver function. Plasma liver enzyme levels were measured immediately preoperatively and again four to eight days after surgery and halothane anaesthesia. Minor elevations of both AST and ALT occurred in four patients but this was not associated with a clinical deterioration in the patients' postoperative recovery. In the children studied pre-existing liver disease did not predispose to a deterioration of liver function following surgery and halothane anaesthesia.