Estrus detection has been cited as one of the most important factor affecting the reproductive success of artificial insemination programs. Various estrus synchronization protocols have been developed to bring a large percentage of groups of females into estrus at a predetermined time. Earlier protocols have involved controlling estrous cycle length in cattle either by extending the life span of the corpus luteum by the use of progestogens or shortening the life span of the corpus luteum by the use of Prostaglandins. The reduced fertility following the earlier synchronization protocols made it necessary to understand ovarian follicular and corpus luteum dynamics in cattle. An increase in this basic understanding and the development of treatment regimes to manipulate ovarian follicular and corpus luteum dynamics over the last decade have resulted in development of better estrus synchronization protocols. These protocols are very promising and have the potential to enhance pregnancy rates and the success of artificial insemination programs.