We evaluated the preventive effects of glutamine-enriched pareneral nutrition on the atrophy and hypofunction of the transplanted small intestines in the rat. Wistar rats received jejunal isografts and central venous catheters for parenteral nutrition (PN) for ten days. Rats received either PN with 3% alanyl-glutamine or the PN with isonitrogenous ballanced nonessential amino acids. Glutamine-enriched PN significantly increased mucosal villous height mucosal thickness, crypt depth and villous surface area compared with the non-glutamine PN. Normal enterocyte ultrastructure of the graft was maintained in the Glutamine-enriched group. Atrophied microvilli and broken mitochondrial crista were observed in the control group. It was found that the amount of absorption of 15N-glycine was greater at the 1st, 2nd, 3rd hour in glutamine-enriched group than that in the control. These results indicate that the glutamine-enriched parenteral nutrition can promote the proliferation of mucosa, maintain the ultrastructure and improve the amino acid absorption in the transplanted small bowel in the rat.