Eighty-one patients with liver disease were studied for the postoperative changes in the arterial blood ketone body ratio (KBR) and routine liver function tests. The postoperative patients were classified into three groups-according to the postoperative changes in KBR. In the 54 patients of group A, KBR did not decrease to below 0.7, only 2 cases with complications (3.7%); in the 25 patients of group B, KBR decreased transiently to 0.4-0.7 and then increased to over 0.7, 9 cases with complications (36.0%), but they were ameliorated concomitantly with the restoration of KBR; in the 2 cases of group C, KBR decreased irreversibly to below 0.4, and a variety of complications occurred, so the patients finally died of multiple organ failure (MOF). It was found that routine liver function tests were less reliable direct indicators for the onset of postoperative hepatic insufficiency than KBR, which reflected the oxidoreduction state of liver mitochondria.