Abstract.The ratio of functional parenchymal (acinar and duct) cells to intracapsular fat and connective tissue in human submandibular salivary glands is seen microscopically to differ from subject to subject. In the present analysis of an apparently age‐related change, a modification of the random‐point counting method of Chalkley (1943) of determining the relative volumes of tissue constituents from histological sections was applied to the submandibular glands of a randomly chosen sample of 36 subjects (six from each decade of age from 25–84 years) from a series of 211 consecutive autopsies. Reproducibility tests of the method of measurement and also observations on a further group of 19 healthy control subjects who had died “sudden” deaths, were made. When the values for the volume, of functional mass of acinar and duct cells relative lo that of fat and connective tissue were analyzed in relation to age, a gradual significant reduction through adult life was found (regression coefficient b =–0.28, p<0.01). Moreover, the values for a further group 5–14 years of age fell close to the extrapolated regression line of the groups aged from 25 to 84 years old. The trend for reduction may therefore begin in childhood. Analysis did not indicate that either fat or connective tissue alone predominated in the replacement of secretory cells. The values were not related to the adiposity of (he subject, and no trend for change with age was found in the fresh wet weights of 60 glands from subjects aged 25–74 years. The evidence indicates an average loss of a quarter of the relative secretory cell volume between childhood and old age, by which time the more extremely affected glands may hav