OBJECTIVE To study the effects of mifepristone on estrogen receptors (ER) and progestin receptors (PR) in human uterine leiomyoma and myometrium. METHODS 20 patients with uterine leiomyoma who had surgical indication received 25 mg of mifepristone daily for 90 days beginning on the first day of menstrual cycle. Ultrasound examination, serum hormonal parameters, liver and renal function, electrolyte, complete blood count were monitored prior to and at the end of treatment. Hysterectomy or myomectomy was performed just when the treatment finished. Leiomyomata and myometrial tissue were obtained for immunohistochemical ER and PR analyses using monoclonal antibody. Control group included 20 patients who had matched age, weight, size and position of leiomyoma, and operated in the follicular phase of the cycle. RESULTS After 90 days of mifepristone treatment, the leiomyoma volume decreased by (37.3 +/- 19.0)% and the uterine volume decreased (27.4 +/- 21.9)%. Hormonal parameters were within the levels of follicular phase. ER and PR positive rate in leiomyoma but not in myometrium of study group were significantly less than those of control group (P < 0.001). The positive rate of ER and PR of control group and PR of study group in leiomyoma were significantly higher than those in myometrial tissue of both groups (P < 0.05). ER of study group in leiomyoma was similar to myometrial tissue (P > 0.05). CONCLUSIONS Mifepristone is a safe and effective drug for treating uterine leiomyoma. It can significantly decrease ER and PR in leiomyoma but not in myometrial tissue.