Complex intracellular inclusion bodies of the Biondi type were observed in the choroidal epithelium (choroid plexus of the lateral ventricle) of a 43-year-old male chimpanzee. The specific components of these inclusions are bundles of filaments 8-15 nm in diameter, which are associated with lipid droplets and a wide variety of unidentified inclusions of differing electron density. Biondi bodies are characteristic inclusions of the choroid plexus of aged humans but have been claimed to be absent from the choroidal epithelium of senescent animals including nonhuman primates. The present finding of Biondi body-like inclusions in an aged chimpanzee underscores the usefulness of nonhuman primates as models for studies of aging, seeking to gain a better understanding of gerontological aspects of the human brain.