Calcineurin inhibitors have significantly improved the one-year graft survival of renal allografts. However, chronic nephrotoxicity caused by calcineurin inhibitors contributes to the long-term decline in renal function in kidney transplant recipients. Approximately ninety percent of the protocol biopsies of renal allografts, performed at 18 months post transplantation, show histological lesions of chronic calcineurin nephrotoxicity . In recent years, two new non-nephrotoxic immunosuppressive drugs, i.e. mycophenolate mofetil and sirolimus, have become available for the prophylaxis of graft rejection in renal transplantation.