BACKGROUND Implanted insulin pumps (IIPs) are an alternative treatment for diabetes mellitus. To maintain good glycemic control, patients with an IIP require frequent surgical interventions. METHODS Since November 1986, 21 patients with insulin-dependent diabetes mellitus at the Johns Hopkins Hospital have undergone implantation of pumps subcutaneously with a catheter delivering insulin into the peritoneal space. Patients were followed up with self-monitoring of blood glucose levels two to four times daily and percutaneous refills of the pump with U-400 insulin every 6 to 12 weeks. RESULTS In 153 patient-years, 77 pumps were placed. The mean pump life was 29 +/- 2 months. Morbidity was limited to pump site infections (3.9%) and one small bowel obstruction. Inadvertent insulin overdelivery has never occurred. Episodes of insulin underdelivery were caused by backflow anomalies (n = 67), which were cleared by percutaneous rinses, or catheter obstructions (n = 12), which required catheter replacements. Ninety-one operations were required to maintain pump function. All patients are alive and report improvements in quality of life. Significant reductions in hemoglobin A1C and plasma glucose levels were also seen. CONCLUSIONS Long-term use of IIPs results in significant improvements in clinical parameters and quality of life for individuals with insulin-dependent diabetes mellitus. Relatively frequent operations are required for maintaining pump function, which are done with a local anesthetic with minimal morbidity.