The aim of this work is to estimate the functional state of the epithelium of the mammalian endometrium at different stages of the sexual cycle. For this purpose was used the scanning electron microscopy and the state of the endometrial cytoskeleton of white rats was evaluated at different stages of the sexual cycle. Firstly, the stage of the sexual cycle was established by using the method of vaginal cytology, and then some of the samples were used to make preparations for scanning electron microscopy and coloration on the cytoskeleton cycle. The number of animals used to study each stage of the sexual cycle was 5. In diestrus, typical atrophy of endometrial cells is observed. During this period, was recorded the intensive output of white blood cells and lymphocytes into the uterine cavity. By the time of the proestrus, the picture changes sharply, the surface of the endometrium increases, due to the formation of full folds. In this case, a large number of microvilli is seen. In metestrous, despite the protrusion of the endometrium, the microvilli do not exert any more. The folds of the epithelium are absent during the period of action of the progesterone, and numerous ducts of the uterine glands are visible on the surface of the endometrium. All these data are consistent with a change in the functional characteristics of the reproductive tract during the estrous cycle.