Posttransplantation diabetes (PTDM) is a frequent complication of tacrolimus (TAC)-based immunosuppressive therapy after kidney transplantation. We investigated whether immediate conversion from TAC to Cyclosporine (CSA) could reverse or at least improve new-onset PTDM. Between February 2002 and February 2004, 28 adult kidney transplant recipients maintained on TAC were diagnosed with new-onset PTDM. Eight adult patients with new-onset PTDM were enrolled in the study and converted from TAC to CSA, the remaining 20 patients served as controls and were continued on the TAC-based immunosuppression. The conversion to CSA was performed immediately after establishing the diagnosis of PTDM at an average of 11 months posttransplantation. We did not document any episodes of acute rejection or worsening renal function after conversion. After conversion to CSA, among the 3 patients started on insulin, 1 has come completely off antidiabetic medications, whereas 1 required decreased doses of insulin, and the third has been converted to oral medications. Of the 5 patients originally on oral medications, 3 completely discontinued therapy, whereas the other 2 were well controlled on single-drug therapy at reduced doses. After a mean follow-up of 17 months, in the control group 9 of the 16 patients started on oral antidiabetics ultimately required insulin treatment and no patient could stop antidiabetic or insulin therapy. These findings indicate that conversion from TAC to CSA is a simple, safe, and efficacious way to reverse or at least improve PTDM.