Ten critically ill, very low birth weight infants less than 30 weeks' gestation were treated with exogenous insulin administered through a continuous insulin infusion pump (Betatron II, Cardiac Pacemaker, Inc). Infants were hyperglycemic to dextrose infusions greater than 6 mg/kg/min. The blood glucose concentration became normal in all infants within two to four hours, with varying requirements for continued insulin treatment. Tolerance to intravenous dextrose increased from a mean of 7.4 mg/kg/min to 11.2 mg/kg/min with glycosuria. Energy intake increased from 49.5 calories/kg/d prior to insulin pump therapy to 70.4 calories/kg/d afterward (P less than .01) with weight gain changed from -23 g/d to +13 g/d (P less than .01). One unexpected observation was the apparent normalization of blood glucose homeostasis on higher dextrose doses among some infants after only one three- to six-hour treatment with insulin. The continuous insulin infusion pump is a flexible tool that allows insulin infusion rates to be changed as dictated by blood glucose values without altering other parenteral infusions.