Need of oxygen by the liver during hypothermic perfusion was evaluated using isolated perfusion model. Livers were perfused by a continuous perfusion system with oxygen saturated perfusate or nitrogen saturated perfusate, or simply stored for 12 hours at 5 degrees C. Quality of individual liver was assessed at one hour after normothermic reperfusion. Tissue edema was significant in all experimental groups, but the extent of which was much higher in nitrogen and simple cold storage groups. AST, ALT, LDH and PNP in the perfusate at the end of normothermic reperfusion were significantly higher in nitrogen and simple storage groups and those of oxygen group were similar to the control. Tissue adenine nucleotide and purine catabolite concentration in oxygen group was almost identical to the control at the end of hypothermic preservation, while ATP and energy charge in nitrogen and simple cold storage groups were significantly low. Conjugated dienes before and after reperfusion showed no difference in any groups, indicating no involvement of free radical injury on reperfusion in this asanguineous perfusion model. These results suggest that continuous supply of oxygen is necessary for liver preservation even though the temperature is lowered to inhibit cellular metabolism.