Subcutaneous continuous insulin infusion systems deliver insulin at a basal rate designed to keep blood glucose levels normal in the non-fed state. Additional insulin is delivered at meal time. Pumps can provide near optimal control of blood glucose concentrations in selected, highly motivated patients. The pump provides better diabetic control than once daily insulin injections, although several daily injections can provide comparable control. Optimal control with the pump causes some short-term beneficial metabolic changes, but there are no controlled clinical trials evaluating the long-term effect on complications. Insulin pump therapy should be initiated only for highly motivated, well instructed patients in a supportive clinical setting. The hazards include rapid development of uncontrolled diabetes when insulin infusion stops, and development of hypoglycemia in the basal rate mode.