Renal ischemia followed by reperfusion leads to acute renal failure in both native kidneys and renal allografts. Cyclosporine A (CsA) has been used as an immunosuppressive agent in organ transplantation. In the present study, the effect of CsA on ischemia/reperfusion (I/R)-induced injury in the kidney was investigated. Ischemia/reperfusion injury caused a significant deterioration in the renal function, morphology and gave rise to a severe oxidative stress in the kidney. At 3 mg/kg i.v., CsA significantly improved the functional and histological parameters and attenuated the oxidative stress induced by renal ischemia/reperfusion. From the results of our study, it can be concluded that low-dose CsA pretreatment preconditions the rat kidneys against subsequent ischemia/reperfusion injury.