The mitogen-activated protein kinase/ERK kinase (MEK)/ERK pathway was shown to be constitutively activated in a large number of acute myelogenous leukemia (AML) cells, suggesting the important roles of this pro-survival signaling in leukemogenesis and proliferation of AML cells. This study explored the impact of the MEK inhibitor AZD6244 on the effect of cytarabien (AraC), one of the most commonly used anti-leukemia agents, to induce growth arrest and apoptosis of AML cells. AZD6244 effectively blocked AraC-induced MEK/ERK activation and enhanced its ability to induce growth arrest and apoptosis of NB4 and HL60 cells in parallel with induction of DNA damage as measured by detection of gamma-H2AX by Western Blot analysis, resulting in enhanced expression of p21( waf1 ) and downregulation of c-Myc and Bcl-xl in these cells. Enhanced induction of apoptosis mediated by combination of AZD6244 and AraC was also shown in freshly isolated AML cells (n = 3). Taken together, concomitant administration of AraC and the inhibitor of MEK/ERK signaling may be useful for treatment of individuals with AML.