Between June 1986 and November 1994, 22 previously transfused patients with severe aplastic anemia (SAA) were treated with high-dose cyclophosphamide (CY) (50 mg/kg over 4 consecutive days) and 7 Gy total lymphoid irradiation (TLI) in two fractions before allogeneic bone marrow transplantation (BMT) from HLA-identical sibling. Graft-versus-host-disease (GVHD) prophylaxis included the combination of methotrexate and cyclosporine A in all cases. Actuarial survival at 5 years is 73 +/- 9 per cent for the entire group and 86 +/- 13 per cent for the seven patients < or = 18 years. The incidence of graft failure was 0 per cent, and of acute GVHD and chronic GVHD was 31.5 per cent and 24 per cent respectively. Prolonged interval from diagnosis to BMT adversely influenced survival (P = 0.03). No hypothyroidism or secondary malignancies have been documented in this series. Our findings indicate that survival with CY-TLI is comparable to that obtained using preparative regimens without radiation. The changing role of radiotherapy in pretransplant immunosuppression for SAA is discussed.