In 1953, Stevens & Leblond published their classical paper on the cell types of the gastric mucosa. Epithelial cells of the mucosa of the fundus were divided, on the basis of their staining reaction with PAS, into surface epithelial cells, mucous neck cells, parietal cells and zymogenic cells. Since then, all these cell types, with the addition of argentaffin cells, have been described in detail with the electron microscope (see, for example, Helander & Ekholm, 1959; Sedar, 1961 a, b; Ito & Win-chester, 1963; Helander, 1964; Lillibridge, 1964). During an investigation of the gastric mucosa in dog and mana cell has been noted which has certain ultrastructural characteristics differing from those already described. The present authors believe that it represents yet another cell type which has many characteristics of an undifferentiated cell and which may function in a reserve capacity. A preliminary report of this work has already been made (Johnson & Young, 1967).