OBJECTIVES: I. Determine the graft failure rate and overall survival of patients with severe aplastic anemia after receiving an allogeneic bone marrow transplant. II. Determine the efficacy of high dose cyclophosphamide and antithymocyte globulin as conditioning regimen for a second bone marrow transplant in patients who reject their first graft. III. Determine the efficacy of methylprednisolone and anti-CD3 monoclonal antibody as a conditioning regimen for a second bone marrow transplant in patients who reject their first graft and are poor candidates for cyclophosphamide and antithymocyte globulin.

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.

PROJECTED ACCRUAL: A total of 40 patients (20 with aplastic anemia and 20 with graft failure) will be accrued for this study.