Moderate to high lymphocyte and polymorphonuclear (PMN) leucocyte infiltrations were observed in the endometrium and myometrium of non-pregnant mice. Similar density of leucocyte infiltrations were observed in post-parturient mice, but there were more macrophages in postparturient than the non-pregnant mice. Three out of 6 non-pregnant and 5 out of 6 post-parturient mice had low PMN leucocyte infiltration in the luminal epithelium. However, in the placentome and interplacentomal part of the uterus of the pregnant mice, leucocytes were absent.