Oviduct specific glycoprotein 1 (OVGP1) also known as pOSP, MUC-9, sOP92, EAP, EGP and OGP, is produced by non-ciliated oviductal epithelium in many mammalian species. After its secretion to the oviductal fluid OVGP1 participates in the final gamete maturation, sperm capacitation, fertilization and supports early embryonic development. Secretion and expression of OVGP1 is regulated by steroid hormones and depends on the oestrus cycle. Molecular analysis of OVGP1 indicated that it is highly conserved at both amino acid and nucleotide levels. The main divergence has been observed in the carboxy terminal region containing deletions, insertions and tandem-repeat sequences containing O- and N- glycosylation sites. The carbohydrates protect OVGP1 protein and modulate its specificity and biological activity. Additionally, other post-translational modifications (phosphorylation, sialic acid residues, sulphation) contribute to the diversity of actions of OVGP1 among different species.