Sex mismatch is a well-known risk factor for chronic rejection of liver allografts, but the mechanisms involved remain unclear. Since experimental observations suggest that female liver is more sensitive to reperfusion injury than male liver, we assessed the influence of gender on oxidative stress. Livers from male and female rats were exposed to warm ischemia and reperfused by an oxygenated buffer. Chemiluminescence was continuously recorded. Reduced and oxidized glutathione and malondialdehyde lactic dehydrogenase values were also determined. Chemiluminescence increased during reperfusion in both groups, but was significantly greater in livers from female rats. Malondyaldehyde and lactic dehydrogenase progressively increased in all animals, reaching significantly greater values in female rats. Livers from female rats showed an increase in all the parameters of oxidative stress compared to male animals. A greater susceptibility to reperfusion injury may be evoked as an alternative mechanism to explain the poor outcome of female organ after liver transplantation.