The oviduct provides the best environment in which a zygote can grow and it can also support the development of embryos from a different species. However, there is no clear explanation of its embryotrophic properties at present. In several species, oviduct epithelial cells synthesize and secrete glycosylated proteins that become associated with developing embryos. Although these macromolecules may have a functional role at the time of fertilization and early embryonic development, the nature of such a role remains to be elucidated. The aim of this work was to perform a comparative analysis of oviduct-specific glycoproteins in search of molecules common to different species since their phylogenetic conservation would imply biological significance. In previous studies, sheep oviduct-specific proteins were characterized and a monoclonal antibody (AFRC MAC 264) specific for the sheep oviduct protein 92 (sOP 92) was produced; hence, sheep was taken as the reference species. The degree of similarity between sheep glycoproteins and those of the cow, goat, pig, rabbit and mouse was determined on the basis of: the presence of carbohydrate side-chains, cross-reactivity with AFRC MAC 264, correspondence of molecular weight between cross-reacting molecules, and similarity of immunohistochemical localization. On this basis, proteins similar to sOP 92 were present in cow and goat oviduct. A more limited similarity was also observed in pigs. This indicates a certain degree of phylogenetic conservation and suggests that these molecules may play an important physiological role; however, their function remains to be determined.