Dietary pyridoxine deficiency in rats significantly reduced (20–43%) the intestinal uptake of D-glucose, glycine, L-alanine and L-leucine. An appreciable reduction in the activities of sucrase, lactase, alkaline phosphatase and leucine amino peptidase was also observed, but maltase activity was unaffected under these conditions. A con-siderable decrease (27–66%) in membrane proteins, sialic acid, phospholipids and free cholesterol fractions in vitamin deficiency was observed. Estercholesterol and triglyceride contents were not affected. Acetate-1- 14C incorporation into various lipid fractions indicated that observed decrease in membrane lipids in B6 deficiency was a consequence of reduced synthesis. It is concluded that pyridoxine deprivation produces marked changes in chemical architecture of brush borders, which probably explains the observed aberrations in epithelial cell function in this nutritional deficiency.