Purpose:To investigate the differences between male and female rats and the effects of sex hormones on tissue changes in the lung and liver in a sepsis model.Methods:Sixty Sprague-Dawley rats were divided into six groups of ten. Groups 1 and 2 were the control male and female groups, respectively, subjected only to sepsis; groups 3 and 4 were the male and female groups, respectively, subjected to sepsis, then given 0.04 mg/kg estrogen + progesterone (E-P) intramuscularly (i.m.); and groups 5 and 6 were the male and female groups, respectively, subjected to sepsis, then given 0.5 mg/kg testosterone (T) i.m. The rats were killed and the histopathological changes in the lung and liver were examined, and plasma endotoxin levels were measured.Results:Histopathological examination revealed less congestion, portal inflammation, and focal necrosis of the liver, and less congestion, edema, and emphysematous and inflammatory changes in the lung in the E-P groups than in the other groups. Moreover, signs of systemic endotoxemia in plasma were proportionally less in the female rats and in the E-P groups than in the male rats and the T groups.Conclusion:Female rats subjected to sepsis showed less liver and lung tissue damage and less systemic endotoxemia than male rats, because of the effects of female sex hormones.