Twenty five infants who were small for gestational age received glucagon (0.5 mg/day by continuous infusion) in the treatment of hypoglycaemia. Twenty responded within three hours with a rise in blood glucose concentration to above 4 mmol/l. Five subjects subsequently required hydrocortisone to maintain glucose concentrations. Rebound hypoglycaemia occurred in nine infants after rapid discontinuation of glucagon or interruption of the intravenous infusions. Response was poor after maternal beta blockade.