This study examined the postoperative plasma endotoxin level, plasma endotoxin inactivation capacity and clinical outcome after administration of an enteral diet supplemented with glutamine, arginine and ω-3-fatty acid in patients undergoing gastrointestinal operations on an prospective, randomized and double-blind design. 40 patients undergoing gastrointestinal operations were randomized into two groups, with each having 20 patients. One group received standard enteral nutrition and the other was fed the formulation supplemented with glutamine, arginine and ω-3-fatty acid. The two groups were isonitrogenous. The infusion was started from day 1 after surgery and continued for 7 days. Blood samples were collected on the morning of day 1 before operation and on the morning of 1, 4 and 7 day(s) after operation and analyzed for plasma endotoxin level and endotoxin inactivation capacity (EIC). Our study found no differences between the two groups on plasma endotoxin level. After surgery a rapid reduction in plasma endotoxin inactivation capacity was observed in both groups, a significant recovery of the plasma endotoxin inactivation capacity was observed on morning of day 4 after surgery in the study group (0.12±0.02 EU/mL and 0. 078±0.022 EU/mL respectively, P＜0.01). Shortened hospital stay was observed in the experimental group (11.7±2.0 days in the control group and 10.6±1.2 days in the experimental group respectively, P=0.03). It is concluded that perioperative parenteral nutrition supplemented with glutamine, arginine and ω-3-fatty acid ameliorated postoperative immunodepression but without direct effect on endotoxemia.