The ductus epididymidis of the dog is lined by a pseudostratified columnar epithelium. The boundary tissue of the epididymis, surrounds the epithelium, and is divided into periductal stroma and tubular interstitium. Principal cells were observed in the luminal surface of the epithelium. Numerous stereocilia lined the luminal surface of principal cells. These results are compared with previous findings observed in the epididymis of other species