We investigated the effect of enteral glutamine on intestinal permeability and bacterial translocation after whole abdominal radiation in rats. Rats irradiated with 10 Gy to the abdomen were randomly divided into a glutamine-free diet group and a glutamine-rich diet (2% glutamine) group. After 3 days of feeding of each diet, the 6-h urinary recovery of polyethylene glycol 4000 was significantly decreased in the glutamine-rich diet group compared to that in the glutamine-free diet group. The 6-h urinary recovery of phenolsulfonphthalein was also decreased in the glutamine-rich diet group, but the difference was not significant. Plasma endotoxin concentration was significantly lower in the glutamine-rich diet group. Twenty-four hour after gavage with 14C-labeled Escherichia coli, the detection rate of 14C-labeled bacteria in the mesenteric lymph nodes of rats was significantly lower in the glutamine-rich diet group. The adherence of 14C-labeled E. coli in the jejunal mucosa was significantly lower in the glutamine-rich diet group than in the glutamine-free diet group, but there were no significant differences in the ileal mucosa. These findings suggest that in rats with intestinal injury induced by irradiation, enteral glutamine maintains the intestinal barrier and reduces bacterial translocation.