To determine the role of intensive chemotherapy and allogeneic bone marrow transplantation (BMT) in treatment of refractory anemia with excess of blasts (RAEB) or RAEB-t (in transformation), the outcome of 37 consecutive children, 12 with RAEB and 25 with RAEB-t, diagnosed between 1985 and 1995 was analyzed. Fourteen patients received intensive chemotherapy according to the AML-BFM protocols 83, 87, or 93 (group 1). Seven patients were treated less intensively with the 6-week consolidation phase as induction (group 2). Allogeneic BMT was performed in 10 children of group 1 and 2 after, and in eight (group 3) without prior chemotherapy. Eight children received minimal or no chemotherapy (group 4). Of 21 children (groups 1 and 2) 17 (81%) achieved complete or partial remission after chemotherapy, 12 of them (10 of group 1) remained in remission, eight after BMT. Five-year survival in 29 children treated intensively (groups 1-3) was 46%, SE 12%. Two of the other eight children (group 4) remained alive, one after spontaneous remission. Outcome after BMT was related to the blast count in the bone marrow prior to BMT. None of 10 children (including two with minimal or no chemotherapy) with < or = 12% blasts before BMT relapsed, in contrast to five of eight patients with a higher blast count (P log rank 0.02). We conclude that a substantial number of children with RAEB or RAEB-t can achieve remission with intensive AML-specific chemotherapy. In patients responding to intensive chemotherapy an increase in long-term survival after allogeneic BMT can be expected.