Design: Successful pancreas transplantation results in insulin independence and normoglycemia. This prospective study was performed to investigate long-term metabolic changes after pancreas transplantation. Methods: Thirty-eight type 1 diabetic patients after simultaneous pancreas/kidney transplantation (SPK) with a pancreas graft survivalfor at least10years were studied in a prospective manner. HbA1c and glucose levels before and during an oral glucose tolerance test (OGTT) were analyzed from 3 months to 10 years after SPK. In addition, insulin secretion and glucagon response were measured. Results: Fasting glucose increased slightly and continuously from 3 months to 10 years (from 78 ± 3 to 91 ± 2 mg/dl). Even HbA1c levels showed a mild but significant increase from 3 months to 10 years after SPK. Glucose tolerance deteriorated markedly 10 years after SPK. Insulin secretion during OGTT remained stable for 10 years. Parameters of insulin resistance and sensitivity did not change significantly but glucagon secretion increased significantly during the course after SPK. Late after SPK, glucagon levels were higher in patients with an impaired or diabetic glucose tolerance. Conclusions: Pancreas transplantation is able to restore endogenous insulin secretion for 10 years or more. Especially, late after SPK, a deterioration of glycemic control was detected, even if glucose values were within the normal range. During prospective long-term follow-up, an increase of glucagon secretion but no decrease of insulin secretion was detected.