Gastric and colonic ileus after major abdominal operation precludes normal oral nutrition in the immediate postoperative period. Since small bowel motility and absorptive capacity are present immediately after operation, the small bowel may be used for feeding. We prospectively evaluated the efficacy of early postoperative jejunal feeding of elemental diet in three groups of patients. Fourteen adults undergoing elective partial colectomy were randomized to receive jejunal feeding of elemental diet (ED) or isotonic intravenous infusions of dextrose (IV). Considering all avenues of nutrition for the first ten postoperative days, seven ED patients received a mean daily input of 2283 calories and 14.1 grams of nitrogen compared to 800 calories and 3.4 grams of nitrogen for the seven IV controls (P less than 0.005). The ED patients lost 2.4 per cent of their body weight during the first postoperative month compared to a 6.1 per cent weight loss for the IV controls (P less than 0.005). The ED group required an intravenous catheter for 1.8 days, compared to 6.6 days for the IV group (P less than 0.005). Twenty consecutive patients subjected to major upper gastrointestinal operations received a daily mean of 1468 calories and 9.7 grams of nitrogen jejunally during the first ten postoperative days. Mean weight loss at two and four weeks postoperatively was 2.8 per cent and 3.5 per cent of preoperative weight. Ten patients received jejunal elemental diet for longer than one month because of postoperative complications or adjunctive therapy for cancer. Mean weight loss was 2.8 per cent. Early postoperative jejunal feeding of elemental diet supplies more nutrients and results in less weight loss than does intravenous therapy with isotonic dextrose. Early postoperative feeding is of value in patients undergoing major operations on the upper gastrointestinal tract.