Several studies have reported that gastrointestinal (GI) intolerance symptoms are the limiting factor to enteral alimentation in the immediate postoperative period and often the reason for resorting to total parenteral nutrition (TPN). We postulated that Reabilan HN (a recently developed small peptide-based formula, in part obtained by enzyme hydrolysis of proteins) might be better absorbed and better tolerated so as to avoid the need for TPN. Accordingly, 19 patients undergoing major abdominal surgery were randomly assigned to receive Reabilan HN via jejunostomy or an equicaloric isonitrogenous TPN regimen. Both were begun 6 hr postoperatively at 25 ml/hr and increased by 25 ml/hr at 12-hr intervals up to the rate providing 1.5 times the calculated REE. GI tolerance to enteral feeding was excellent during the first three postoperative days, allowing the progression of the feeding rate to 99% of goal. During the next 3 days (starting on average 1.7 days after the return of bowel sounds), GI intolerance symptoms required a reduction in feeding rate to 52% on average. Subsequently, the symptoms resolved and the feeding rate reached 96% of goal. Although overall mean daily calorie and nitrogen intakes were lower for the enteral than for the TPN group (79.6 +/- 10.2% vs 94.6 +/- 3.8% of goal; p less than 0.01), the enteral group was nevertheless in positive caloric and nitrogen balance, and maintained similar serum albumin, prealbumin, and plasma transferrin levels. Average daily cost of supplies was $44.36 for enteral vs $102.10 for parenteral nutrition (p less than 0.001). We conclude that enteral feeding using this formula is well tolerated and cost-effective in the immediate postoperative period.(ABSTRACT TRUNCATED AT 250 WORDS)