Inadequate leukemic ablative therapy ending in leukemic relapse is the source of most failures following bone marrow transplantation. Attempting to improve pretransplant leukemic ablative therapy, we report on a pilot regimen that includes teniposide, the principal chemotherapy, and total-body irradiation. Ten patients with acute lymphoblastic leukemia in relapse underwent allogeneic bone marrow transplantation. All patients engrafted. Toxicity, primarily mucositis, was manageable. Two patients have survived for 1547 and 1988 days in continued remission. Eight patients have died: three from sepsis in the immediate posttransplant period, four with recurrent leukemia, and one with chronic graft-versus-host disease and pneumonia. We believe that these results support further trials with teniposide in pretransplant leukemic ablative therapies.