New onset diabetes is a major complication after kidney transplantation. However, the natural course of posttransplantation diabetes mellitus (PTDM) remains unclear. The aim of this study was to demonstrate the detailed natural courses of PTDM according to the onset and persistency of hyperglycemia, and to investigate risk factors for development of different courses of PTDM in renal allograft recipients. The purpose of this study is to develop novel immune suppressants for PTDM using of action mechanism of them. The use of immunosuppressive drugs in transplanted patients is associated with the development of diabetes, possibly due to ${eta}$-cell toxicity. To better understand the mechanisms leading to post-transplant diabetes, we investigated the actions of prolonged exposure of ${eta}$-cells to therapeutical levels of tacrolimus (FK506) or cyclosporin A(CsA). The immunosuppressive drug cyclosporine(CsA) is a potent agent widely used after organ transplantations and various autoimmune disorders. After using CsA, some patients suffer severe complications including renal and vascular toxicity. The renal or vascular toxicity is influenced by the degree of the endothelial damage. FK506(tacrolimus) is a widely used immunosuppressive agent in the treatment of various medical conditions, including autoimmune disease, bone marrow and organ transplantations. We found some interesting clusters and confirmed the feasibility of cDNA microarray in the study of Immunosuppressant. In this study, we investigated gene expression patterns induced by Immunosuppressant in RIN-m5F of rat insulinoma cell line. Gene expressions evaluated using cDNA microarry in two clusters were increased or decreased. this study provides comprehensive comparison of the patterns of gene expression changes induced by CsA and FK506 in ${eta}$-cells. This study could establish that the mode of action mechanism by which currently used insulin inhibitors inducing PTDM could be elucidated at least in part, which raises the possibility that novel immune suppressive PTDM can be developed. The molecular biological study on PTDM will also contribute the progress in diabetes research field as well as in that of PTDM.