Volunteers for this study must be women between 12 and 55 years of age who have been diagnosed with aplastic anemia (with a platelet count of less than 50,000/microliter) and currently have active uterine bleeding. Candidates must not be pregnant or breastfeeding, must have a uterus and at least one functioning ovary, and must be willing to use nonhormonal methods of birth control (such as condoms or a diaphragm) for the duration of the study. On the first visit, candidates will be screened with a complete medical history (including obstetric and gynecological history) and will undergo a physical examination, a pelvic exam and a pelvic ultrasound. Blood and urine samples will also be taken on this first visit.