This review discusses current immunohistochemical and lectin histochemical approaches to identify and to distinguish the different epithelial cell populations of the pulmonary tissue. Special emphasis is given to the characterization of pulmonary alveolar and bronchial epithelial cells and mesothelial cells. Structural proteins, membrane molecules and secretory products of the alveolar epithelium, which have already been characterized and which may be useful for monitoring the developmental or pathological processes, are listed and briefly described.