Continuous subcutaneous insulin infusion has provided patients who have diabetes with a system for achieving treatment targets with a lower incidence of severe hypoglycemia. Patients prefer the flexibility, convenience, and physiologic glycemic control of continuous subcutaneous insulin infusion. Future insulin pumps will be implanted within the body and the “loop” will be closed, providing a physiologic insulin delivery system. This system will provide the means for achieving near-normal glycemia, limit episodes of severe hypoglycemia, and prevent long-term complications of diabetes mellitus.