Two patients with severe aplastic anaemia received bone-marrow transplants from unrelated donors selected for HLA compatibility. Graft-versus-host disease occurred in both patients but responded to treatment. Both patients had stormy courses after grafting, but subsequently their conditions improved, and one was not receiving any treatment at follow-up after day 330 while the other had mild chronic graft-versus-host disease at day 150. These results show that unrelated, histocompatible volunteers may successfully donate marrow for the treatment of severe aplastic anaemia, though many problems remain to be solved.