Parotid acinar cells from ad libitum-fed and starved rats were studied using electron microscopic and cytochemical techniques. Lysosomes containing acid phosphatase and non-specific esterase activity were present in cells of both ad libitum-fed and starved rats. They included lipofuscin-like bodies, smaller round or irregularly-shaped bodies, multivesicular bodies, and coated vesicles. After 16–24 hours of starvation, lipid droplets had accumulated in the basal cytoplasm, and secretory granules showed evidence of degeneration. These altered granules consisted of irregular clumps of dense material in a less dense matrix. After 48–72 hours of starvation, the altered granules increased in number and fused to form large aggregates. Some of the aggregates also contained vesicles, membranous material, and lysosomal residues. The altered granules and aggregates were reactive for acid phosphatase and non-specific esterase. The formation of the altered granules appeared to occur by spontaneous degeneration of the secretory granules, with secondary fusion with pre-existing lysosomes and other altered granules. The results suggest that the lysosomal system of the parotid acinar cell functions to segregate and digest secretory granules during periods of reduced secretory stimulation.