Monitoring of minimal residual disease (MRD) has become a strong diagnostic tool in acute lymphoblastic leukemia (ALL).It is used for risk adapted therapy and for the recognition of pending relapses.In acute myeloid leukemia (AML), there is still a need for more suitable MRD markers.A stepwise approach which combined genome wide expression profiling and a TaqMan realtime PCR based screening was used to identify new markers for the monitoring of MRD in AML.Leukemic cells from 52 children with AML were analyzed.Seven genes were identified which are vastly overexpressed in many patients with AML compared to healthy bone marrow: CCL23, GAGED2, MSLN, SPAG6, and ST18 as well as the previously described markers WT1 and PRAME.The expression of all genes decreased to normal levels in patients who achieved a continuous complete remission.Elevated levels of at least one gene were found prior to relapse in 7 out of 10 patients who relapsed.This set of genes should allow a sensitive and specific monitoring of MRD in AML.Notably, some of these markers couldalso serve as therapeutic targets or might be involved in leukemogenesis.MSLN is already used as a target for immunotherapy in clinical trials in other malignancies.In the ongoing multi center study AML-BFM-2004 for pediatric AML we are prospectively analyzing the prognostic relevance of this MRD monitoring.So far samples of 72 patients were analyzed.