Embryo attachment to the apical surface of the uterine epithelium is an event found in all mammalian species. Consequently, aspects of this process may be shared and considered as general principles in implantation strategies across species. This review focuses on studies implicating mucin glycoproteins disposed at the apical surface of uterine epithelia as antiadhesive molecules that block embryo attachment. As such, mucins must be removed, at least locally, to permit intimate contact between trophectoderm and uterine epithelia. Subsequently, we consider the role that heparan sulfate proteoglycans (HSPGs) and HSPG-binding proteins play in tethering embryos to the apical surface of uterine epithelia during the attachment process.