Thirty-one patients with acute non-lymphocytic leukemia (18 patients) or with high-risk refractory acute lymphocytic leukemia (13 patients) underwent bone marrow transplantation between March 1980 and March 1990. The high-dose conditioning regimen employed included cyclophosphamide followed by fractionated total body irradiation (12 GY). Fourteen patients who had an HLA-identical sibling donor received allogeneic bone marrow transplantation (allo-BMT); the other 17 patients received autologous bone marrow transplantation (auto-BMT) purged with 4-hydroperoxycyclophosphamide (4HC). Four of the 14 allo-graft recipients died of leukemic relapse and 2 others died of graft-versus-host disease. Three of the 17 auto-graft recipients died of relapse and 1 suffered relapse in the testes. The actuarial risk of relapse was 29% for the allo-BMT patients and 24% for the auto-BMT patients (P less than 0.05). The event-free survival rate at five years was 57% and 74% respectively (P less than 0.05). Although there was no difference between them, a trend toward a higher survival rate and a lower mortality and morbidity was observed in the auto-BMT group. These results suggest that autologous bone marrow transplantation purged with 4HC is an effective and useful treatment for children with acute non-lymphocytic and lymphocytic leukemia who have no HLA-identical donor.