Between November 1986 and January 2000, 28 patients with insulin-dependent diabetes mellitus were enrolled in the implanted insulin pump study at Johns Hopkins Hospital. An additional two patients underwent pump implantation under compassionate use guidelines due to apparent resistance to subcutaneously administered insulin uptake. The mean patient age was 44 +/- 10.5 years. Eleven patients (39%) were female and the mean duration of diabetes was 25.7 +/- 8.9 years. Diabetic retinopathy, neuropathy, and nephropathy were present in 43%, 25% and 11 % of patients, respectively. The insulin pumps functioned safely for a total of 189 patient years. Mean pump life was 26 +/- 1.2 months. There was no mortality. Morbidity was limited to pump-site infections [n=y (4%) of all pumps placed], one case of pump migration and skin erosion, and one small bowel obstruction associated with the pump catheter. Mean serum hemoglobin AIC levels before and after pump placement were 9.0 +/- 2.9% and 7.5 +/- 0.7% (P=0.0023), respectively. Correspondingly, the mean daily blood glucose levels decreased from l61 +/- 40 mg/dl before placement to 141 +/- 27 mg/dl after pump placement (P=0.0063). Intraperitoneal delivery of insulin by a mechanical pump appears to be an attractive alternative for the treatment of insulin-dependent diabetes mellitus.