The ultrastructural changes in the ejaculatory duct epithelium in Glossina morsitans morsitans Westwood was examined for special features related to spermatophore formation; special attention was paid to the cytoplasmic organelles and the plasma membrane specializations (apical infoldings and space formation). Internally, the transportation system is characterized by a cuticle-lined lumen bordered by cuboidal cells. The endoplasmic reticulum is scarce, while mitochondria are distributed throughout the cytoplasm. At the cuticular surface of the cells, extensive apical infoldings are associated with numerous mitochondria. Glycogen granules are found only in the cytoplasm of teneral flies. Apically, adjacent cells are tightly apposed; however, prominent intercellular spaces develop (1 to 7 days), permeate most of the epithelium and connect to the basal surface of the cells. These are features characteristic of transporting cells believed to have an absorptive function. As the adult fly ages, the ultrastructural characteristics of the epithelium change and are typified by the disappearance of glycogen granules and the formation of intercellular spaces. The features of the ejaculatory duct are discussed briefly in terms of their role in spermatophore formation.