We treated five patients with Type II diabetes by means of a subcutaneously implanted intravenous insulin pump and compared their metabolic response with that observed during conventional insulin therapy. The use of the pump improved control of glycemia, as manifested by reductions in mean plasma glucose (from 188±46 to 106±12 mg per deciliter [mean ±S.D.]), fasting glucose (from 187±42 to 80±13 mg per deciliter), and postprandial glucose (from 287±74 to 182±29 mg per deciliter), together with a diminution of glycemic excursion and normalization of glycosylated hemoglobin A1 (from 12.1 ±2 to 8.0±1 per cent). At the end of the study the pumps had been in place for a mean of 7.0 months (range, 5.5 to 9.7 months) without mishap and with good patient acceptance. Our data suggest that improved blood glucose control can be achieved by means of a permanently implanted continuous insulin-infusion device in ambulatory patients with Type II diabetes who require insulin, and that the need for daily insulin injections can thereby be eliminated. (N Engl J Med. 307; 1982:265–70.) A CAUSAL relation between hyperglycemia and microvascular complications of diabetes is strongly suggested by animal studies, but the available clinical studies are inconclusive.1 2 3 4 5 6 7 8 Conventional modes of subcutaneous insulin therapy have failed to prevent the vascular complications associated with long-term diabetes, perhaps because normoglycemia has not been achievable by these methods of therapy or because subcutaneous insulin may be less physiologic than intravenously administered insulin. Although mechanical devices fall short of providing total endocrine replacement, they offer the advantages of mass production; furthermore, such devices do not produce the immunologic complications of transplantation therapy. Studies to date of portable insulin-delivery systems.