New-onset diabetes after transplantation (NODAT) or posttransplant diabetes mellitus is a frequent metabolic complication of organ transplantation. Diabetes incidence rates among transplant recipients are higher than in the general population. The estimated rates are 9-18% after kidney, 20-33% after liver, 26-40% after lung, and 29% after heart transplants, respectively. In retrospective studies, NODAT was associated with higher costs of posttransplant care and increased risks of graft failure, infection, cardiovascular disease, and death. The incidence of NODAT is influenced by both traditional risk factors for type 2 diabetes (age, family history, obesity, hepatitis C infection, and ethnicity) and transplant-specific risk factors. Managing NODAT is challenging because posttransplant care is complex and characterized by multiple variables including immunosuppressive regimens, choice of antidiabetes agents, and optimal use of insulin therapy. Therefore, predicting and preventing NODAT would be a compelling objective for improving care of posttransplant patients. During the pretransplant period, lifestyle modifications in patients at risk for NODAT should be considered, recognizing that no randomized controlled trials exist to inform specific modalities or cost-effectiveness of such an approach. After hospital discharge, close monitoring of blood glucose during the first month, and every 3 months thereafter for the first year, is recommended for those without prior history of diabetes mellitus. Future areas of investigation include clinical validation of NODAT risk score engines, validation of interventions for primary prevention of NODAT, the development of immunosuppressive regimens with minimal diabetogenic effects, and prospective determination of the role of glycemic control on graft survival and cardiovascular outcomes.