Nature and potential functions of chemical signals involved in the process of pregnancy recognition in cattle are discussed. The array of prostaglandins, steroid metabolites, and proteins produced by the conceptus and endometrium are described and collated with histological and physiological responses of the uterus and ovary that lead toward maintenance of the corpus luteum. Advances during the last 10 yr partially have identified the conceptus-endometrial-ovarian signal sequence that is associated with maternal recognition of pregnancy in cattle. Final evaluation of the control system should permit investigators to improve embryo survival and augment further the impact of embryo manipulation to improve genetic merit of the cattle population.