Firstly, the ultrastructure of the caveolated cells on the rat bile duct were examined by a transmission and a scanning electron microscope. Next, the author seeked whether caveolated cells were present or not in the human digestive organs. Lastly, functional study of the caveolated cells on the rat bile duct were investigated using horseradish peroxidase and pilocarpine. Then the facts mentioned below were clarified. 1) Caveolated cells in the rat bile duct were found most densely at the divelticulum-like recesses but on the luminal surface except this recesses caveolated cells were found partly densely and partly sparsely. 2) On the rat, the straight filaments of the caveolated cells of the bile duct were less developed than that of the digestive tract, but circular filaments were more developed than that of the digestive tract. 3) The apical vesicles of the caveolated cells were revealed to have no communication to outer lumen of these cells using lanthanum as a tracer. 4) The caveolated cell-like cells were found in the mucosa of a human colon. But these cells could not be identified clearly with caveolated cells. Because the vesicles were scanty and small in size and the inner substance was relatively electron opaque. 5) After intraluminal injection of peroxidase into ligated segments of bile duct, the marker was found within the apical vesicles. But it was not uncertain whether pre-existing apical vesicles had taken up the marker or vesicles containing the marker were formed newly by pinocytosis. 6) After intraperitoneal injection of pilocarpine, the supranuclear vesicles began to expand and the vesicles with granules moved toward the free surface suggesting eruption or diacrine secretion. And frequently apocrine secretion was also observed. In conclusion, the author supposes that caveolated cell may have both absorptive and secretory functions and this type cells may present in human digestive tract.