OUTLINE: Patients with graft failure with the following organ function and performance status are assigned to arm I: Performance status: Karnofsky 60-100% Pulmonary: FEV1 and DLCO at least 50% Cardiac: Left ventricular ejection fraction at least 45% Hepatic: None to mild venoocclusive disease Patients with graft failure with the following organ function and performance status are assigned to arm II: Performance status: Karnofsky 20-50% Pulmonary: FEV1 or DLCO less than 50% Cardiac: Left ventricular ejection fraction less than 45% Hepatic: Moderate to severe venoocclusive disease Patients with aplastic anemia are assigned to arm I. Arm I: Patients receive cyclophosphamide IV over 1 hour on days -5 to -2, antithymocyte globulin IV over 8 hours on days -5 to -3, and bone marrow transplant on day 0. Arm II: Patients receive methylprednisolone IV twice a day on days -5 to 62; monoclonal antibody OKT3 IV on days -1 to 24; bone marrow transplant on day 0; oral cyclosporine twice a day starting day 20; and filgrastim (G-CSF) subcutaneously once a day starting day -5 until blood counts recover. Patients are followed once a week for 3 months and then monthly for one year.