Twenty-one patients with acute leukemia in second to fifth remission were treated with bone marrow transplantation: 19 patients with transplants from HLA-matched siblings and two with transplants from identical twins. Twelve patients survived from 15 to 1,625 days after transplantation: six of 11 in the ALL group and six of 10 in the AML group. Recurrence of leukemia after marrow transplantation occurred in five patients. The cause of death in five patients was infection, in two patients combined with graft-versus-host disease. Long-term disease-free survival can probably be achieved in 30%-35% of all patients with acute leukemia who receive a marrow transplant in second or subsequent remission.