We retrospectively reviewed the course of 1,000 renal transplants performed in 835 recipients (758 nondiabetics) to assess the incidence of new onset posttransplant diabetes in former nondiabetics. A total of 119 (15.7%) recipients manifested posttransplant diabetes, of whom 64 (53.8%) became hyperglycemic within 3 weeks of transplantation. Actuarial survival analysis indicated a statistically significant selection of blacks; 68 (57.1%) in the group of posttransplant diabetics contrasted with 30.4% of the overall series who were black (p = less than 0.01). Males comprised 73 (61.3%) of posttransplant diabetics, consistent with the male proportion of 66.6% in the entire series. The total dose of methylprednisolone administered before onset of posttransplant diabetes was less than 2.5 g in 86 (69%) and less than 5 g in 110 (92%) patients. Familial diabetes had been noted in 12 (10%) posttransplant diabetics and in 10 (9%) controls. New cases of posttransplant diabetes occurred at a relatively constant annual rate over the decade of study (+/- 15%/year). Patient survival in controls was greater than in posttransplant diabetics, reaching significance (83 vs. 67%) at 2 years. Kidney graft survival in controls and posttransplant diabetics was similar. We conclude that posttransplant diabetes is of greater prevalence in blacks, is not proportional to total dose or duration of intravenous methylprednisolone therapy, and imposes a threat to recipient survival.