Previously we have identified multiple surges in plasma concentrations of gut hormones postnatally in enterally fed term and preterm infants. In this study on 104 preterm infants we have shown that such surges are induced after ingestion of very small quantities of human milk. Whereas 6-day-old exclusively parenterally fed infants showed no postnatal elevation in enteroglucagon, gastrin, GIP, motilin and neurotensin, infants recovering from hyaline membrane disease who had received restricted enteral nutrition had similar hormone surges to those seen in well infants on full enteral feeds. Significant elevations in enteroglucagon, gastrin and GIP occurred after a cumulative mean enteral feed volume since birth of only 24 ml (12 ml/kg body weight) had been consumed and after a mean total intake of 96 ml (50 ml/kg) the response was maximal. Greater feed volumes were required to produce a neurotensin or motilin surge, but even these volumes were substantially lower than those required for full enteral feeding. In view of the proposed roles of gut hormones in the adaptation to extrauterine nutrition these data have implications for mammalian biology and raise the possibility that 'minimal enteral feeding' might have a clinical therapeutic role in infants undergoing prolonged parenteral nutrition.