Rat liver was kept at 4°C or 37°C in MEM, and reperfused through a closed circulation from the hepatic vein to the portal vein at 37°C with the same solution. Although purine nucleoside phosphorylase and ALT activities were increased in the perfusate, depending on the duration of ischemia at both 4°C and 37°C, the ratio of the latter to the former was significantly higher after 37°C-ischemia than after 4°C-ischemia. The stimulation stage of Kupffer cells evaluated in situ by formazan deposition after liver perfusion with nitro blue tetrazolium and phorbol myristate acetate was elevated after 4°C-ischemia longer than 1 h, but not after 37°C-ischemia. In contrast, the degree of oxidative stress in hepatocytes assessed by formazan deposition after liver perfusion with nitro blue tetrazolium alone was greater after 37°C-ischemia than after 4°C-ischemia. These results suggest that oxidative stress in hepatocytes and the stimulatory state of Kupffer cells after ischemia-reperfusion may differ between 4°C-ischemia and 37°C-ischemia, probably leading to different development of liver damage.