Patients with acute lymphoblastic leukemia who have poor prognostic features at diagnosis usually have a short disease-free survival in spite of successful remission induction. Those poor risk features are: age over 30 years, a white blood cell count over 25,000/microliter, certain translocations of chromosomes, and requirement for more than six weeks of induction chemotherapy to attain a complete remission. We have used high-dose radiochemotherapy to prepare 39 patients with acute lymphoblastic leukemia in first complete remission (1 infant and 38 adults; median age 23 years) for bone marrow transplantation from histocompatible sibling donors. Thirty-one of the 39 patients in this study had one (n = 23) or more (n = 8) poor risk features: age (n = 7); high white blood cell count (n = 19); translocations (n = 4), or resistance to initial induction therapy (n = 11). Currently, 26 patients are surviving for 4-72 months (median 18 months) following marrow grafting and are in complete remission. One of the surviving patients had two marrow transplant procedures because of recurrent leukemia. Actuarial survival in complete remission is 63% for the entire group of 39 patients and is 60% if the eight patients who had no poor risk features are excluded from analysis. The following causes for failure were observed: leukemic relapse was encountered in four patients between 3 and 17 months after BMT for an actuarial relapse rate of 16%; bacterial sepsis was the cause of death in two patients; graft-versus-host disease and/or interstitial pneumonia led to the demise of seven patients, and one patient died with leukoencephalopathy. It appears that high-dose radiochemotherapy followed by bone marrow transplantation from a histocompatible sibling donor during first complete remission can result in a high disease-free survival rate for younger adults with poor-risk acute lymphoblastic leukemia. This concept needs to be tested in prospective trials comparing bone marrow transplantation with chemotherapy.