To improve long-term kidney graft function, acute graft rejection, hyperlipidemia, hypertension, and toxic influences must be avoided because they may contribute to chronic allograft nephropathy. Many studies have demonstrated greater efficacy and tolerability of tacrolimus compared with cyclosporine with regard to these conditions. Our study investigated whether 30 patients with deteriorating renal function benefitted from conversion to tacrolimus based upon a retrospective analysis using data recorded from 3 years before to 3 years after conversion. Renal function (GFR) deteriorated progressively under cyclosporine (creatinine: baseline 1.5 mg/dL; delta(Cyc) = +1.4 mg/dL within 3 years; GFR: delta(Cyc) = -35 mL/min within 3 years). After switching to tacrolimus, kidney function stabilized and even improved (creatinine: baseline after switching 2.9 mg/dL; delta(Tac) = -0.7 mg/dL; GFR: delta(Tac) = 14 mL/min). Conversion from cyclosporine to tacrolimus is recommended for patients with a kidney transplant in which there has been a progressive decrease in renal function. It may lead to stabilization of or even improvement in transplant function.