The objective. To assess the effect of Ulipristal acetate (UA) in the dose of 5 mg/day on the endometrium over a 12-week period in patients with uterine leiomyoma. Patients and methods. We examined 30 patients with symptomatic uterine leiomyoma aged 28 to 50 years (mean age 37.7 ± 7.6 years). Clinical and ultrasound data were analysed before and after treatment with a selective progesterone receptor modulator (SPRM). The Pipelle biopsy of the endometrium before and after treatment was performed, histological and immunohistochemical examination with determination of optical density and relative expression of progesterone and estrogen receptors, Bcl-2, Ki-67, p53, PTEN. Results. Against the background of SPRM therapy menometrorrhagia stopped quickly, the size of fibroid nodules decreased significantly, in 76.7% the endometrium underwent therapeutic pathomorphosis and corresponded to the prolifetative type. After the course of SPRM therapy we noted a higher relative expression of estrogen and progesterone receptors, low levels of КІ-67 expression, higher expression of PTEN in the endometrial stroma, absence of changes in Bcl-2 and p53 expression. Conclusion. UA has a pharmacological effect on the endometrium in patients with uterine leiomyoma, inducing therapeutic pathomorphosis. Enhancement of the expression of sex steroid hormones and the prevalence of Ki-67 expression in the endometrial glands as compared with the stromal component account for the mechanism of a fast control over metrorrhagia. A higher expression of the antiapoptotic marker PTEN along with invariable values of the expression of the apoptosis inhibitor Bcl-2 and the tumour suppressor p53 in histogenetic structures of the endometrium condition the benign character of the ongoing morphological changes.