Although intraluminal nutrition presumably maintains small intestinal mass by direct contact with the epithelial cells, hormonal or neurovascular elicited by feeding may play an indirect role. In order to test for the presence of indirect factors, Thiry- Vella fistulae were created from the proximal small intestine of two groups of rats. The bypassed gut of a group of rats receiving an elemental diet intravenously was compared to a second group receiving the same diet by intragastric infusion. After 1 week, there was significantly greater (P less than 0.01) gut weight, mucosal weight, DNA content, and protein content of both the gut in continuity and tje bypassed gut of intragastric infused rats. Total sucrase activity was also greater (P less than 0.01) in intragastric fed rats, and this was due to both a greater protein content and specific activity (P is less than 0.05) of the gut in continuity and to the greater protein content of the bypassed gut. Serum gastrin levels were similar (P less than 0.05) in both groups, suggesting that gastrin may not play a role in initiating the differences reported. This study suggests that intraluminal nutrition maintains the small intestinal epithelial population in part, indirectly, by unidentified hormonal or neurovascular stimuli.