PIP: RU-486, the first clinically available antiprogestin, has numerous gynecologic applications beyond first-trimester pregnancy termination. Long-term administration of 2 mg/day of RU-486 suppresses ovulation while maintaining serum estrogen levels and ovarian follicular activity. In the endometrium, long-term RU-486 administration results in significant endometrial dysynchrony and stromal compaction. RU-486 has been demonstrated to relieve pain in women with symptomatic endometriosis and decrease the size of uterine leiomyomata by about 50%. There are preliminary findings indicating that RU-486 is effective in the treatment of premenstrual syndrome, ectopic pregnancy, and anovulatory uterine bleeding. In need of further investigation is the RU-486 dosage that can treat pathophysiologic states while minimizing the endometrial effects.