One aim of the AML-BFM 98 study was to evaluate prospectively the impact of matched sibling donor (MSD)-SCT in 1st complete remission (CR) in children with high-risk (HR)-AML. Patients: Between 7/1998 and 3/2004 494 children and adolescents were enrolled in the studies AML-BFM 98 and the AML-BFM 98 Interim 2003. Patients with favorable cytogenetics [t(8;21), inv(16), t(15;17)], corresponding morphology (AML FAB M1/2 with Auer rods, M4eo, M3) and Treatment: All patients received double induction and consolidation. MSD-SCT in 1st was scheduled after 4 blocs of treatment. Children who were not transplanted in 1st CR received intensification and a 1-year maintenance therapy. The recommended conditioning regimen consisted in busulfan and cyclophosphamide. Results ITT analysis revealed no significant differences in of 5 year disease-free survival (DFS) and overall survival (OS) between children with or without a donor (no donor vs. donor: DFS 43±4% vs. 47±7% plog rank 0.52; OS 56±4% vs. 58±9%, plog rank 0.16). The as-treated analysis gave similar results: CHT only vs. MSD-SCT: DFS 35±11% vs. 59±9% p Mantel-byar 0.13; OS 59±13% vs. 62±12%, p Mantel-byar 0.51). The major reasons of treatment failures were relapses in all groups [CHT only n=100 (52%), MSD-SCT n=13 (34%), MUD-SCT n=9 (50%)]. A 2nd CR was achieved in 71% of the CHT only group (n=74). After SCT in 2nd CR, OS was 40±6%. By contrast, only two children (9%) of 22 children after relapse following SCT in 1st CR could be salvaged. Severe late adverse events (e.g. severe chronic GvHD CTC grade IV, destruction of big joints, intracerebral bleedings) were more frequent in children transplanted in 1st CR (15%) than in those with CHT only (including SCT in 2nd CR; 5%, p×2 Conclusion: In the population-based, prospective multi-center study AML-BFM 98 allogeneic MSD-SCT in 1st CR showed no advantage in children and adolescents with HR-AML. Considering the higher toxicity of allogeneic SCT, in the ongoing trial AML-BFM 2004, this SCT (MSD or MUD) is restricted to patients in 2nd CR and refractory AML.