Successful pregnancy requires well-coordinated interactions between the maternal uterus and the developing embryo in pigs. In pigs, implantation begins around Day 12 of pregnancy. During this period, conceptus undergoes a dramatic morphological change and secretes various factors such as estrogens, interleukin-1 beta (IL1B), and interferons. Estrogens produced by conceptuses act as the signal for maternal recognition of pregnancy, and the mechanism of estrogen action is explained by the endocrine and exocrine theory. The uterine endometrium becomes receptive to the conceptus by changing cell adhesion molecules, polarizing epithelial cells and increasing secretory activity. Some changes of uterine activity are affected by the ovarian hormone, progesterone, but the presence of conceptus in the uterus also induces changes of endometrial functions, including most importantly maternal recognition of pregnancy. Many factors, such as hormones, cytokines, enzymes, extracellular matrix proteins, and transport proteins are reported to be present at the maternal-fetal interface and function in the establishment of pregnancy in pigs. However, understanding of the cellular and molecular events occurring in the endometrium is not complete. In recent studies we made some progress on understanding of expression and function of genes involved in maternal-fetal interaction for the establishment and maintenance of pregnancy in the uterine endometrium in pigs. Firstly, we found that lysophosphatidic acid (LPA) was present at the maternal-and fetal interface at the time of implantation and LPA receptor 3 was uniquely expressed in the endometrium during early pregnancy. Secondly, we observed that salivary lipocalin (SAL1), a lipid-binding protein, was uniquely expressed in the uterine endometrium at the time of embryo implantation, and its expression was regulated by IL1B. Furthermore, expression of IL1B receptors are regulated by estrogen and IL1B, and IL1B functions in expression of genes related to prostaglandin synthesis and transport. Thirdly, we found that calcium regulatory molecules TRPV6 and S100G were dynamically regulated in the uterine endometrium during pregnancy, suggesting that regulation of calcium ion concentration may important for the embryo implantation and the maintenance of pregnancy. Finally, we observed that an MHC class II molecule, SLA-DQ, is expressed in the uterine endometrium at the time of conceptus implantation and its expression is essential for successful pregnancy, indicating that appropriate maternal-fetal immune interaction is required for the maintenance of pregnancy. Further analysis of these molecules will provide insights into the cellular and molecular basis of maternal-and fetal interaction during pregnancy in pigs.