Many producers who raise horses find breeding horses rewarding, yet frustrating. Mares and stallions are traditionally placed in the breeding herd due to successful performance records, with little consideration for their reproductive capabilities. Horses are difficult breeders with an estimated foaling rate of below 60 percent. Various factors contribute to this and basic understanding of equine reproductive physiology can improve reproductive efficiency and foaling rates. The breeding manager's goal should be to get the maximum number of mares pregnant, in the shortest amount of time, and to deliver a live, healthy foal each year.