The objective of this study is to evaluate the effects of 10 mg and 25 mg doses of asoprisnil, compared to placebo, taken daily for 12 weeks, on uterine blood flow and the morphology of the endometrium and uterine fibroids.

No medical therapy is currently available for the long-term treatment of uterine fibroids. The objective of this study is to determine the effects of asoprisnil in uterine fibroid growth suppression. Full thickness biopsies obtained from surgical procedures will allow the assessment of asoprisnil's effects on the basalis, the myometrium, and on endometrial angiogenesis. Various other exploratory immunohistological and biochemical specimens will be collected to evaluate the mechanisms of action of asoprisnil in the endometrium, the myometrium, and in uterine fibroids.

Inclusion Criteria:

• Premenopausal women, at least 18 years of age
• Diagnosis of uterine fibroid(s), confirmed by ultrasound
• History of menstrual cycles between 17 and 42 days
• Otherwise in good health
• Scheduled for a hysterectomy at the end of the treatment period
• Negative pregnancy test
• Agrees to double barrier method of contraception
• Pap test with no evidence of malignancy or pre-malignant changes
• Endometrial biopsy with no significant histological disorder

Exclusion Criteria:

• Less than 3 months after having a baby or breast-feeding
• Any abnormal lab or procedure result the study-doctor considers important
• Severe reaction(s) to or are currently using any hormone therapy
• History of cancer or alcohol or drug abuse
• Diagnosis of Polycystic Ovary Syndrome
• History of prolactinoma
• Current use of Intrauterine Device
• Significant gynecological disorder
• Uterine size > 32 weeks gestation
• Current diagnosis of endometriosis
• Uterine artery embolization within 6 months