To determine the effect of small enteral feedings on small bowel function, 46 infants with birth weight less than 1500 g, selected on the basis of risk factors for feeding intolerance, were assigned randomly to one of two feeding groups. Group 1 received low-volume enteral feeds (12 ml/kg/day) in addition to parenteral alimentation for 10 days beginning on day 8 of life; group 2 received parenteral alimentation alone until day 18 of life. After this trial period feedings were increased by 15 ml/kg/day in all infants. Four infants (9%) developed necrotizing enterocolitis (one prior to any feeds, two in group 1, and one in group 2); two others were dropped from the study for reasons unrelated to feeding. The remaining 18 infants in group 1 had improved feeding tolerance compared with the 22 in group 2, as manifested by fewer days that gastric residuum totalled more than 10% of feedings (1.3 +/- 0.5 days vs 3.2 +/- 0.6 days, respectively, p less than 0.05) and fewer days that feedings were discontinued because of feeding intolerance (2.7 +/- 0.8 days vs 5.5 +/- 0.9 days, respectively, p less than 0.05). Consequently, 17 of 18 (94%) infants who had received the early low-volume enteral feedings achieved an enteral intake of 120 kcal/kg/day by 6 weeks of life, whereas only 14 of 22 (64%) infants in the delayed feeding group reached this intake (p less than 0.05). Peak total serum bilirubin concentrations were comparable in the two groups. The initiation of hypocaloric enteral substrate as an adjunct to parenteral nutrition improved subsequent feeding tolerance in sick infants with very low birth weight.