In pregnancy, the endometrium represents the hosting surface for invading semi-allogeneic cells. A very fine tuning of cellular interactions is indispensible for the successful symbiosis of mother and fetus. Such interactions include a variety of immune cells, which are present in extremely high concentrations, and trophoblast cells. A wide spectrum of soluble and surface molecules is involved in homing, activation and switching of lymphocyte functions, but also in regulation of embryo implantation and control of trophoblast invasion. This mini-review provides a brief overview of immunological features of the endometrium.