Background: Immunonutrition has been demonstrated to modulate gut function, reduce infectious complications, hospital stay, and ventilator days in the critical patients. Aim of the study: We assessed the effect of immunonutrition for the prevention of intestinal mucosal atrophy, apoptosis, and bacterial translocation in head injured rats. Methods: Thirty five rats were randomised into 5 groups. Following moderate closed head injury, in Group 1; Standard Enteral Nutrition, Group 2; Immunonutrition, Group 3; TPN, Group 4; pe. saline were applied. Group 5 was control group (chow-fed). The rats were sacrificed and segments of the ileum were removed for histologic examination, and samples of tissues taken for microbiologic evaluation. Results: Both intestinal apoptosis and mucosal atrophy were significantly lower in Group 2 and Group 5 (p < 0.008). Bacterial translocation was significantly lower in Group 2 than Group 1 (p < 0.008). Conclusion: The enteral immunonutrition prevents intestinal barrier function in brain injured rats. (C) 2003 Elsevier Science Ltd. All rights reserved.