In pigs, the peri-implantation period is recognized as determinant of successful reproduction, and it is controlled by neuroendocrinal interactions among signals originating from the female hypothalamic-pituitary-ovarian axis, uterus, and developing embryo. The transcriptomic activity of the pituitary gland may influence reproductive processes occurring in pigs during the peri-implantation period. The aim of this study was to determine alternations in gene expression in the porcine pituitary gland during the peri-implantation period (days 15-16 of pregnancy) in comparison with that during the respective days of the estrous cycle using a microarray approach. Overall design: We analized anterior pituitary glands obtained from 8 indyviduals (n=8). Pituitaries were collected from mature gilts on days 15-16 of early pregnancy (n = 4) and the estrous cycle (n = 4).