The study evaluates a new medical treatment for fibroids using the progesterone receptor modulator CDB-2914. A similar compound, mifepristone (Registered Trademark), reduced fibroid size when given for twelve weeks. This study will compare fibroid size, hormone levels and symptoms before and during daily administration of CDB-2914 (10 or 25 mg) or placebo for 10 - 14 weeks. To do this, women will undergo MRI and a saline hysterosonogram (ultrasound with fluid) of the uterus before and at the end of the treatment; they will have blood drawn every 7 - 14 days, and will fill out a symptom calendar at home. Hysterectomy will be performed at the end of the treatment to evaluate the effects of the medication on the uterine and fibroid tissues, and to provide treatment for the study participant. Women will be randomly assigned to the treatment groups; during the treatment period neither the participants nor the investigators will know the type of treatment that a woman receives.