We investigated the role of CD25 as a prognostic marker in acute myeloid leukaemia (AML). Seventy-two newly diagnosed patients ≤60 years were retrospectively analysed by flow cytometry for CD25 positivity of AML blasts. Patients with CD25 expression of >10%, when compared to ≤10%, had a significantly shorter overall survival (OS, p = 0.0005) and relapse-free survival (RFS, p = 0.005). In multivariate analysis CD25 expression is an independent adverse factor for OS and RFS. High CD25 combined with FLT3-ITD positivity resulted in the poorest OS and RFS (p = 0.001 and p = 0.003, respectively). CD25 expression remained prognostic within the intermediate cytogenetic risk group. In addition, after the first cycle of chemotherapy, a significantly higher MRD frequency was found in patients expressing CD25 above cut-off (p = 0.003). Our results show that CD25 expression is an independent adverse prognostic marker in AML patients ≤60 and correlates with MRD. © 2009 Elsevier Ltd. All rights reserved.