Alternative donor bone marrow transplantation (BMT) to treat severe aplastic anaemia (SAA) in children and young adults has been complicated by high rates of graft rejection and severe graft-versus-host disease (GVHD). We hypothesized that increased immunosuppression combined with T-cell depletion of the marrow graft would enable successful use of unrelated donor BMT in this disease. Preconditioning consisted of cytosine arabinoside, cyclophosphamide, and total body irradiation (TBI). T-cell depletion was with the anti-CD3 antibody T10B9. GVHD prophylaxis consisted of cyclosporine A. 28 previously transfused patients were transplanted. Nine donor/recipient pairs were HLA matched. As of 1 January 1996, 15/28 (54%) patients are alive, transfusion independent and well with a range of follow-up of 13 months to 8 years (median 2.75 years). Fatalities include all three patients with nonengraftment and all three patients with grade III/IV GVHD. Other fatalities were due to infections or therapy-related toxicity. The incidence >or= grade II acute GVHD was 28%. These data show that in children with SAA who have failed immunosuppression, unrelated donor BMT offers a reasonable hope of long-term survival.