Between 1980 and 1985, 175 patients with acute leukaemia in first or subsequent complete remission (CR) were treated by chemotherapy or chemoradiotherapy followed by transfusion of autologous bone marrow cells that had been collected days or months previously. In 85 cases, autologous marrow cells were treated ex vivo with cytotoxic drugs or monoclonal antibodies with the intention of removing residual leukaemic cells. The actuarial relapse-free rate was 52% at 2 years. Of 89 patients autografted for acute non-lymphocytic (myeloid) leukaemia (ANLL), 60 were treated in first remission and 18 in second CR; their relapse-free rates at 2 years were 67% and 41% respectively (P less than 0.001). In contrast, of 77 patients autografted for acute lymphoblastic leukaemia (ALL), 32 were treated in first CR and 28 in second CR and their actuarial relapse free rates at 2 years were 56% and 55% respectively (P = NS). There was no significant difference in leukaemia relapse rates between patients autografted with purged and those autografted with non-purged marrow cells. These preliminary results suggest that autologous bone marrow transplantation may be valuable if offered to patients with ANLL in first CR or to patients with ALL in first or second CR but the need for marrow purging remains uncertain.