The first feed of breast milk given to a group of 12 term infants was previously shown to increase the levels of blood glucose and plasma insulin, growth hormone (GH), gastrin, and enteroglucagon. We have now studied the effects of the first feed of breast milk in two similar groups of preterm infants, to compare the results with those obtained for the term infant. One group of 8 preterm infants received a bolus (2.5 ml/kg) of breast milk via a nasogastric tube; the other group of 5 infants received a continuous intragastric infusion (2.5 ml/kg per hour) of breast milk. No change occurred in the concentrations of blood glucose, lactate, pyruvate, or ketone bodies, or in plasma insulin, GH, pancreatic glucagon, or enteroglucagon in either the 'bolus fed' or the 'infusion fed' group of preterm infants. Thus the marked metabolic and endocrine changes in term infants after the first feed do not occur in preterm infants with standard methods of feeding.