Fifty samples of endometrial tissue from healthy women with regular menstrual cycle and from patients with uterine myoma, ovarian cystoma, uterine hypoplasia and endometriosis were studied. The amount of cytoplasmic (total and free) and nuclear estradiol-binding sites as well as estradiol (E2) concentration in the endometrial cells were estimated. Level of E2 in the peripheral blood plasma did not correlate with its content in endometrial cells. At the same time, amount of cytoplasmic estrogen receptors bound with E2 did not correlate with the estradiol content in cytoplasm. The data obtained suggest the leading role of the cytoplasmic estrogen-receptors interaction in development of hormonal effect on the tissue. The formation of hormone-receptor complexes appears to be controlled by some additional factors of unknown nature.