New-onset diabetes after renal transplantation (PTDM), a common consequence of immunosuppression, is associated with reduced patient survival. However, we know little about the impact of less marked changes in glucose homeostasis. To investigate this problem, we used data on average random blood glucose values during the first, second, and third months posttransplantation, derived from a cohort of 1186 patients who received their first cadaveric or living-donor transplant between 1984 and 2002. We analyzed both patient and death-censored graft survivals, subgrouping recipients into those with end-stage renal failure due to diabetic nephropathy versus those with PTDM versus patients without diabetes. We confirmed that PTDM patients display reduced survival following transplantation, but a long-term survival similar to that of patients with diabetic nephropathy and end-stage renal disease. However, among patients without diabetes, random blood glucose was also a strong determinant of outcome, even when in the low normal range. In contrast, neither the presence of diabetes nor random glucose levels showed a significant impact on graft survival. PTDM is recognized to be an important, potentially modifiable, risk factor for cardiovascular disease in transplant recipients. Our data suggest that there is a gradation of increased risk associated with impaired glycemic control that affects patients who do not have diabetes. These data support the need for improved understanding of glycemic control in transplant recipients and for more detailed screening for impaired glucose tolerance in this population.