Twenty-one patients weth severe aplastic anaemia were evaluated at a single hospital between 1972 and 1975. Patients without histocompatible donors were treated conventionally with androgens, corticosteroids, and HLA-matched platelet and granulocyte transfusions. Bone-marrow transplantation was performed in patients with HLA-identical siblings. The two groups had comparable clinical and haematological prognostic indicators and received similar supportive therapy. All nine patients who were not transplanted died. Median survival in these patients was 82 days (range 21-545). Seven of the twelve (58%) transplant recipients were alive at 120 days--greater than 930 days (p less than 0.04). The one-year actuarial survival of the transplant group was 53%. This study shows that bone-marrow transplantation is a rational alternative to conventional therapy in selected patients with aplastic anaemia.