Equine embryo transfers have increased dramatically in the past decade, but in spite of the advantages of cryopreservation of equine embryos, this technology has not increased proportionally. Lack of a superovulation protocol for mares and the inability to freeze embryos >300 μm have been the limiting factors impeding equine embryo cryopreservation. Data from both controlled laboratory settings and commercial embryo transfer facilities have shown that small embryos can be slow cooled or vitrified and, after thawing and transfer, provide pregnancy rates of 50%–70% similar to that obtained with bovine embryos. In contrast, studies have shown that embryos >300 are damaged more during slow cooling or vitrification than those 300 μm.