Morphometric examinations were made on hematoxylin-stained paraffin sections of 43 human submaxillary glands, in order to determine and describe histological changes of this organ during the aging thereof. The number of fat cells per unit area increases in the first decades, whereas that of the striated ducts decreases. Obviously, striated ducts differentiate earlier than serous acini, with the former thus being less subject to involution with aging than the latter. In old age, the nuclei of the epithelial cells of serous acini and striated ducts are characterized by the formation of certain classes of size, of which the association with polyploidization is, however, questionable. In a 44-year-old male, differences in the size of nuclei between different striated ducts of one section, which were due perhaps to functional peculiarities, indicated the existence of inactive and active glandular regions. The volume density of serous acini decreases continuously in the course of life, while that of the striated ducts decreases in the first decennia only. On the other hand, there was observed a continuous increase in the volume density of fat cells in the entire course of life and an increase of the volume density of connective tissue in the second half of life. The mucous fractions were observed to increase up through the fifth decade of life, after which they were seen to decrease continuously.