Patients with chronic pancreatitis who undergo total pancreas resection inevitably become diabetic unless their islets are autotransplanted to prevent diabetes. We studied patients who underwent this procedure to assess its long-term efficacy in providing stable glucose regulation. Six patients were followed for up to 13 (6.2 ± 1.7) years after intrahepatic islet autotransplantation. From 290,000 to 678,000 islets were transplanted and no patients received drugs to control glucose levels postoperatively. Islet function was assessed by measurements of fasting plasma glucose (FPG), intravenous glucose disappearance rate (KG), HbA1c, insulin responses to intravenous glucose and to arginine, and insulin secretory reserve. Patients were studied two to four times each to obtain longitudinal data. Five of six patients remained free of insulin treatment and maintained FPG <126 mg/dl and HbA1c levels <6.5%. As a group, they maintained stable insulin secretory reserve, but insulin responses to glucose tended to decrease over time in three patients. KG values correlated significantly with the number of islets originally transplanted. These data indicate that intrahepatic autoislet transplantation can successfully maintain stable β-cell function and normal levels of blood glucose and HbA1c for up to 13 years after total pancreatectomy as treatment for chronic painful pancreatitis. This usually overlooked procedure of intrahepatic islet transplantation designed to prevent diabetes in patients undergoing pancreatectomy for chronic pancreatitis should be considered more often.