 Our laboratory has a long-standing interest in viruses that affect the bone marrow, especially those causing bone marrow failure. One specific syndrome, hepatitis-associated aplastic anemia, suggests that the same agent is responsible for the severe and sometimes fulminate hepatitis as well as the profound bone marrow failure. This study is designed to collect clinical data, and samples from patients with hepatitis-associated aplastic anemia, in order to learn more about the clinical features of the disease, as well as to collect blood, liver, bone marrow and stool samples where possible for ongoing virological studies. For liver and bone marrow samples, material will only be obtained when the liver or bone marrow are biopsied for other medical indications, or during the removal of the liver at the time of transplantation. No additional risk to the patient should result from either procedure. 