Technical Abstract: Choosing the best synchronization protocol depends on the goals of individual operations. Syncro-Mate-B is no longer available for synchronization, but a new prostaglandin (PGF) has been added to the market (ProstaMate). Heifers have traditionally been synchronized with the melengestrol acetate (MGA)/PGF protocol that includes feeding MGA for 14 d followed by an injection of PGF 17 d later. Extending the injection of PGF to 19 d after MGA in recent studies has increased synchronization, conception and pregnancy rates. Feeding MGA for 7 d followed by an injection of gonadotropin releasing hormone (GnRH) on d 8 and PGF on d 15 has resulted in equal synchronization, conception and pregnancy rates as the traditional MGA/PGF protocol. The most popular protocol for cows is the GnRH/PGF protocol (GnRH followed 7 d later with PGF). Heifers or cows should be inseminated as close to 12 h after the onset of estrus as possible. Timed AI produces acceptable pregnancy rates 72 h after PGF with the MGA/PGF protocol. Timed AI can also be used 48 h after PGF with the GnRH/PGF protocol if a second injection of GnRH is also given at the time of AI. Nutrition, heat detection accuracy and efficiency, timing of AI, clitoral stimulation after AI, and transportation are factors that can affect the success of an AI program. Bull fertility, bull to cow ratio and pasture size are factors that can affect the success of a synchronization with natural service program.