Background: previous trials have shown that perioperative immunonutrition could protect patients from infectious complications after gastrointestinal cancer operations. the purpose of this study was to determine whether perioperative immunonutrition decreases postoperative morbidity,especially infection complications, mortality and length of hospital stay in patients undergoing major gastrointestinal tract surgery.Methods: one hundred patients with ap lanned elective operation for benign or malignant gastrointestinal illness were randomized into two groups: group 1) oral supplementation for five days before and five days after surgery with 900 mL/day of aformula enriched with arginine, gamma-3-fatty acid and rna +liquid diet ad libitum on one and two postoperative day and then solid food (immunonutrition group; n=50) or group 2) no artificial nutrition before and after surgery,onone and two postoperativeday intravenous solution of 5% glucoseand electrolytes and then normal diet (conventional group; n=50).Results: the groups were comparable for all key baseline and surgical characteristics. there were nine (18%) infectious complications in both groups. overall complication rates were 28% (n =14) in the immunonutrition group and 24% (n =12) in the conventional group. No significant difference between the groups was found in complication rates, mortality or length of hospital stay.Conclusion: routine perioperative immunonutrition to the patients undergoing major gastrointestinal surgery is not beneficial.