The present study was undertaken to investigate whether an amino-acid solution or a mixture of amino acid and sugar could have a nutritive effect on the intestinal mucosa. Self-emptying blind loops of rat jejunum were perfused 3 times daily for 24 or 31 days, through a tube conveyed subcutaneously to the back of the neck, with a Ringer solution or a saline containing methionine and glucose or methionine alone. Methionine infusion induced a significant rise in the villus height of the mucosa of the blind loops, which was accompanied by an increased glucose absorption, as determined in vivo. In mucosal homogenates there was a tendency toward an increase in dipeptidase activity but not in disaccharidase level. Infusion of a mixture of glucose and methionine led to lengthened crypts, as well as larger villi. Glucose transport was again increased, and there was a small rise in both dipeptidase and disaccharidase activities.