We experienced a case of a second renal transplantation patient. With the use of cyclosporin, he lost his first graft because of chronic rejection; with the use of tacrolimus, his second graft suffered from drug nephrotoxicity. On his second renal transplantation, his graft function deteriorated and required haemodialysis with the use of tacrolimus. Repeated biopsies did not reveal the typical characteristics of acute tacrolimus nephrotoxicity and acute rejection. His tacrolimus trough level was not high during the clinical course; however, by reducing tacrolimus dosage, his graft function eventually recovered to mild renal dysfunction. This observation was helpful for clinical diagnosis of the functional toxicity of tacrolimus. The case is interesting in considering the functional toxicity of tacrolimus and the difference between tacrolimus and cyclosporin in terms of immunosuppressive and nephrotoxic actions.