The current work aimed to apply immu-nohistochemistry (IHC) to evaluate the differential distribution pattern of some biologically active proteins in the ductus deferens (DD) in two different animal species common in the Egyptian farms. Immunolocalization of S100, angioten-sin converting enzyme (ACE), α- smooth muscle actin (α-SMA), connexin 43 (Cx43) and galactosyltransferase (GalTase) was practiced on paraffin-embedded sections of DD from clinical-ly healthy adult five donkeys and five water buffalo bulls. The DD, in both species, was lined by a folded, high cuboidal (in donkey) or tall columnar (in buffalo) pseudostratified epithelium with stereocilia. IHC revealed that all antibo-dies used, displayed variable reactivi-ties in the two species. Nerves and the periductal smooth muscles expressed a strong immunoreactivity (IR) for S100 and α-SMA respectively; both in the donkey and in the buffalo. Stereocilia of principal cells showed a marked ACE-immunostaining in the donkey but not in the buffalo. Cx43-binding sites were found between the basal portions of the ductal epithelium and the subjacent in-terstitium; as well as among the peri-ductal smooth muscle cells (SMCs) only in the buffalo bulls. Distinct GalTase-binding sites were found in the ductal epithelium only in the donkey. In con-clusion the present findings exhibited a species-specific pattern of distribution for most of proteins under study, sug-gesting a variable functional signific-ance of the DD in the different animal species.