Over a 10 year period, we transplanted 63 patients with acute lymphoblastic leukaemia (ALL) who had achieved first complete remission (CR). All were > 15 years old and 45 (71%) had at least one poor prognostic factor. Twenty-nine patients with a suitable sibling underwent autologous bone marrow transplantation (BMT). Beginning in 1984, patients without a donor received an allogeneic BMT (34 patients). Preparation consisted of cyclophosphamide (CY)/TBI (78%) or melphalan (Mel)/TBI (22%); marrow was treated in vitro in 31 patients (allogeneic: 7; autologous: 24). Kaplan-Meier estimates of the probability at 6 years of relapse, survival and DFS were 41% (allogeneic: 10%, autologous: 65%, p < 0.05), 44% (allogeneic: 62%, autologous: 26%, p = NS) and 42% (allogeneic: 62%, autologous: 27%, p < 0.06), respectively. This report confirms that allogeneic BMT permits long-term remissions giving high levels of survival when performed shortly after entering first CR while autologous BMT, when performed in the same setting, is less successful at preventing relapse. This study also confirms the high sensitivity of ALL to the graft-versus-leukemia effect provided by allogeneic BMT. Chemoradiotherapy dose intensification delivered at autologous BMT is not sufficient to prevent relapses. Autologous BMT must therefore be augmented by other approaches of which immunotherapy may be one.