Encapsulation of mammalian preimplantation embryos has its origins in the work of Willadsen in the late 1970s and in the need to develop an artificial zona pellucida for denuded sheep, horse, and cattle embryos used in the production of monozygotic twins for the livestock industry. Although functional, these early methods relied on embedding in nonbiodegradable materials, and ultimately, they saw little widespread application. More recently the idea of embryo encapsulation has been revisited as a possible solution to technical problems encountered with human in vitro fertilization and embryo transfer, in hopes of improving embryonic implantation rates. The studies reviewed here represent the current status of mammalian embryonic encapsulation and the preliminary work done using animal models prior to attempting encapsulation for human embryos for infertility therapy.