OBJECTIVE To investigate the effects of continuous early enteral nutrition (EEN) supplemented with glutamine and arginine on gut barrier function in patients with severe acute pancreatitis (SAP). METHODS Thirty two patients with a diagnosis of acute pancreatitis predicted to develop severe disease were randomized into 2 groups: EEN group (n = 18) and EEN + glutamine and arginine group (enteral immunonutrition group, n = 14). EEN was initiated when homeostasis was achieved within 72 hours after attack, and both group received isocaloric isonitrogenous nutrition. Glutamine and arginine were administered into jejunum in the enteral immunonutrition group. Serum amylase, plasma diamine oxidase (DAO), C-reactive protein (CRP), plasma endotoxin, urinary excretion of lactulose (L), and mannitol (M) were measured, and APACHE-II scores were recorded on days 1, 7, and 14. Complications, and length and cost of hospitalization were recorded as well. RESULTS EEN and enteral immunonutrition were both tolerated well. There was no difference in APACHE-IIscore between the two groups (P > 0.05). The DAO, CRP, plasma endotoxin, and urinary L/M levels decreased with the course of SAP. However, the plasma endotoxin and urinary L/M on day 7 of the enteral immunonutrition group were (10.0 +/- 3.8) EU/ml and 0.29 +/- 0.15 respectively, both significantly higher than those of the EEN group [(7.9 +/- 2.8) EU/ml and 0.16 +/- 0.08 respectively, both P < 0.05]. The length of hospital stay and cost showed no differences between the two groups. CONCLUSIONS EEN is safe and feasible in treatment of SAP. Enteral immunonutrition containing glutamine and arginine improves the gut barrier function by reducing the gut permeability and decreasing plasma endotoxin level in the early stage of SAP.