Managing the equine estrous cycle is a common procedure performed by many broodmare managers and veterinarians. Copious research has elucidated many aspects of the equine estrous cycle and allowed veterinarians the tools to manage a mare’s cycle to provide the optimal breeding times, effectively use artificial insemination, induce ovulation, synchronize mares, induce superovulation, advance the onset of the breeding season, terminate pregnancy, as well as a manage a host of other reproductive conditions and diseases. In this article Dr. David Scofield reviews the use of progesterone and estradiol (P&E) therapy in the mare.