The effects of vaneless centrifugal pump (Bio-pump P-80) on energy metabolism were studied, as compared with the roller pump, in an isolated porcine liver perfused with human blood for 6 hours. According to preliminary examination, flow rates were decided to 0.4, 0.8 ml/min/g in roller pump group, in Bio-pump pump group, respectively, not to increase more than 15 mmHg in initial portal pressure. During the perfusion, actual portal pressure was measured and circulatory resistance (portal pressure/flow rate) was calculated before perfusion and hourly after perfusion. Acetoacetate, beta-hydroxybutyrate, lactate and pyruvate, were measured at same times, from which values the ketone body ratio (acetoacetate/beta-hydroxybutyrate, KBR), reflecting the redox state of liver mitochondria, was calculated. In the Bio-pump group, in spite of its high flow, circulatory resistance was low at every hour during the perfusion. KBR was increased rapidly from 0.40 to 1.39, 2.59, 2.75, 2.38, 2.41, and 1.82 and lactate was decreased rapidly from 7.96 to 3.90, 1.77, 1.29, 1.33, 1.34, and 1.25 mmol/L at the respective hours after perfusion. There were significant differences at 2 and 4 hours after perfusion in KBR and after 2 hours of perfusion in lactate as compared with the roller pump group (p < 0.05). These results suggested that the Bio-pump is available for constant and high flow to the liver and helpful to elevate the mitochondrial NAD/NADH ratio (oxidized and reduced forms of free nicotinamide-adenine dinucleotides), leading to and enhancement of metabolic capacity of the perfused liver.