We analysed probability of disease free survival (DFS) and remaining in remission (POR) in evaluable patients with hematological malignancies undergoing allogeneic bone marrow transplantation by Nagoya BMT groups between 1976 and August 1989 according to conditioning regimens retrospectively. Patients were divided into good risk patients with acute leukemia in first remission or CML in chronic phase and high risk patients with advanced disease. The results are as follows: 1. DSF and POR in good risk patients was 45% and 68% at 7 1/2 years for thirty nine patients treated by CY + TBI, 63% and 78% at 5 2/3 years for thirty nine patients treated by CA + CY + TBI, 84% and 84% at 2 years for sixteen patients treated by preconditioning regimens without TBI respectively. 2. DFS and POR in high risk patients was 21% and 45% at 6 years for twenty nine patients treated by CY + TBI, 23% and 48% at 4 5/6 years for forty patients treated by CA + CY + TBI, 64% and 74% at 2 years for eight patients treated by preconditioning regimens without TBI respectively. 3. There were no statistical differences among these conditioning regimens in good and high risk patients. These results show that more effective and stronger preconditioning regimens are needed especially for high risk patients for prevention of posttransplant leukemia relapses.