Recent studies have shown the remarkable gender differences in the susceptibility or expression of many diseases. The mechanism underlying the gender differences is unclear. In the present study, we evaluated the effects of gender differences and different ischemia time on the renal ischemia-reperfusion injury (IRI). The IRI was induced in the bilateral kidneys of 156 male and 30 female BALB/c mice. Renal function, serum creatinine and blood urea nitrogen, and pathology of the kidneys were examined at 24 hr after IRI. Renal IRI was generated successfully in 182 of 186 mice with a 97.85% success rate. The levels of serum creatinine and blood urea nitrogen were significantly increased in male mice subjected to 30 min, 35 min, or 45 min of renal ischemia and in female mice subjected to 75 min of renal ischemia, compared to the control group at 24 hr after operation. In males following 35 min or 45 min of ischemia and in females following 75 min of ischemia, typical acute tubular necrosis was found in the areas of corticomedullary junction and the histopathologic scores, which represent the degree of renal tissue injuries, were significantly increased. In view of our data, the kidneys of male are much more susceptible to IRI than those of female. The optimal ischemia time of kidney is 35-45 min in males and 75 min in females for generating a stable model of IRI in mice. Investigation of the gender differences might provide a new area for mechanistic study of renal IRI.