The incidence and risk factors for the development of posttransplant diabetes mellitus (PTDM) was retrospectively evaluated in cyclosporine-treated renal transplant patients. An incidence of 9.4% was observed over a 10-year period. Weight and body mass index were risk factors identified in a case-controlled study. Age, race, family history of DM, and cyclosporine and prednisone doses were not associated with the development of PTDM. We concluded that the development of PTDM is mainly related to weight. All efforts must be taken to avoid this complication.