We present our experience with bone marrow transplantation (BMT) in 30 consecutive patients with high risk acute lymphoblastic leukemia. With a median follow-up of 4 years the disease-free survival (DFS) was 44% for the whole group, with a significant difference between patients in first or second complete remission (CR 1 and 2, as one group), compared with patients with more advanced disease (greater than CR2), 69.5% versus 15.4% (p less than 0.01). The main cause of BMT failure was leukemic relapse, with a relapse rate of 15% for patients in CR 1 and 2 and of 77% for patients with greater than CR2 (p less than 0.01). Among patients with active disease at BMT those who had 15% blast cells or less in the marrow fared better than those with more advanced disease or extramedullary relapse. Transplant-related death was 17%. Graft-versus-host disease (GVHD) was associated with an antileukemic effect; the DFS for patients with acute and/or chronic GVHD was better than for patients with no GVHD at all.