The ovarian hormones, estrogen and progesterone, and their receptors, the estrogen receptor (ER) and progesterone receptor (PR), orchestrate the complex sequence of events required for uterine receptivity and the establishment of pregnancy. The actions of ER, PR, and other steroid hormone receptors (SHRs) direct the uterus through the processes of implantation and decidualization. Due to the ethical concerns of studying pregnancy in humans, genetically engineered rodent models have facilitated many of the discoveries that have elucidated the molecular events directing early pregnancy. This chapter will cover the conserved structure and function of the SHRs. ER and PR will be highlighted for their pivotal roles in uterine receptivity, implantation, and decidualization. The dynamic regulation of ER and PR expression and activity throughout the estrous cycle and early pregnancy, and the importance of SHRs in coordinating paracrine signaling between the endometrial compartments will also be explored. Finally, the roles of androgen receptor (AR) and glucocorticoid receptor (GR) in the establishment of pregnancy will be discussed.