The present study describes pathomorphological and immunohistochemical findings on uterine serosal inclusion cysts. The material obtained from two female dogs after postpartal ovariohysterectomy. Macroscopically: the cysts with 1-4 mm diameter were present dorsally on the left uterine horn of one of the two animals, whereas cysts of 2-5 mm diameter were detected dorsolaterally on the right horn of the other animal. Microscopically: the cysts revealed a distinct capsule and were surrounded by hyperemic vessels of the subserosa. The inner wall of the cysts was covered by a single-layered flat to cuboidal epithelium. Immunohistochemically estrogen positive cells were detected especially in the uterin glands and ovarial follicles. Epithelial cells belonging to the cysts reacted also positively with anti-cytokeratine sera.