In this study the entire epithelial lining of tracheas and a 15-cm segments of small intestine were dissociated into individual cell components after 45-minute incubation with 1% pronase. Light and electron microscopy of isolated cells confirmed good morphologic preservation of various epithelial cell types dissociated from the trachea and small intestinal mucosa. Of particular interest was the recovery and preservation of APUD endocrine cells, which are known to be widely dispersed amongst various non-endocrine epithelial cells in both the trachea and small intestine. The APUD cells were demonstrated in dissociated cell preparations by a formaldehyde-induced fluorescence method, Grimelius' silver nitrate stain, and electron microscopy. The isolated APUD cells retained their characteristic features, e.g., amine-handling properties, argyrophilia and cytoplasmic dense-core vesicles. The cell dissociation method described in this report provides high yields of viable epithelial cells in single cell suspensions which are suitable for further cell separation into homogeneous populations of single kinds of cells, including the APUD endocrine cells. Availability of methods for isolation of tracheal and intestinal APUD cells will facilitate further studies, in vitro, on secretory, metabolic and functional aspects of these cells.