Macrophages in the lamina propria at the tips of small intestinal villi in 41 of 51 macaque monkeys were filled with eosinophilic, autofluorescent, periodic acid-Schiff-positive globules, hematoxyphilic and Feulgen-positive granules, vacuoles, and iron and lipochrome pigments. The Feulgen-positive granules were seen ultrastructurally in macrophages of nine of 15 clinically normal macaques and baboons. Four of the 15 had similar granules in the intercellular spaces of the epithelium. Ultrastructurally, the eosinophilic globules were electron-dense phagolysosomes; the Feulgen-positive granules resembled nuclei of lymphocytes in various stages of pyknosis. Cytoplasmic organelles enclosed in membrane-bound vacuoles were present in the intercellular spaces of the epithelium of one monkey. Similar organelles were phagocytized by macrophages in another monkey. Feulgen-positive granules have been reported in villi of normal rodents. In all other species, including man, degenerating nuclei called "karyolytic bodies" and other evidence of enterocyte or lymphocyte degeneration have been considered abnormal concomitants of irradiation and antimitotic therapy. The significance of the findings in monkeys is not known, but they may represent a subclinical disease process.