Tuft cells in the rat were fairly numerous in the non-secretory columnar epithelium of the narrow cardial zone on the border of the forestomach. They were also encountered in the gastric superficial and foveolar epithelium and in the epithelium of the cardial glands and more thinly dispersed in the epithelium of the duodenal villi. Each cell possessed a strongly developed microvillus tuft of about 90 microvilli and showed a fibrillary hexagonal core structure; the filaments of which continued in thick bundles far into the cytoplasm. The cytoplasmic structures showed a cytocavitary network, phagosomes, multivesicular bodies, lysosomes and a well developed Golgi apparatus. Glycogen granules were demonstrated in the cells of adult animals, but no phenomena indicative of fat absorption were established. The functional role of different cell organelles and structures is discussed.