Superoxide dismutase (SOD) activity was evaluated by measuring superoxide scavenging capability with the aid of an electron spin resonance (ESR) spin trapping method in a swine orthotopic liver transplantation (OLT) model. The animals were divided into two groups, depending on the length of the survival periods: the short survival group (n = 8) survived less than 6 days and the long survival group (n = 15) 6 days or longer. SOD activity was significantly lower in the short survival group than in the long survival group after reperfusion (P < 0.01). During the period of cold preservation, a minimal change in SOD activity was noted, regardless of the length of preservation. Serum aspartate aminotransferase (AST) levels after reperfusion and serum lactate dehydrogenase (LDH) levels 1 h after reperfusion were significantly higher in the short survival group than in the long survival group (P < 0.01 and P < 0.05, respectively). The difference in polymorphonuclear leukocytes (PMN) was significantly greater in the short survival group at 1 h after reperfusion (P < 0.01). The authors conclude that superoxide scavenging activities in the graft reflect the magnitude of reperfusion injury, which can be a reliable parameter for the estimation of graft outcome.