Studies in the 1990s identified a link between extracellular Nm23 proteins and acute myeloid leukaemia (AML). Confidence in the importance of these observations was undermined by a lack of appreciation that extracellular Nm23 proteins were relevant to either normal or pathophysiology coupled with the lack of demonstrable activity of Nm23 proteins against human AML cell lines. However, independent studies have highlighted the importance of Nm23-H1 in AML and have identified an elaborate Nm23-H1-mediated cross talk between cells within the AML clone. In other studies, roles for Nm23-H1 have now also been implicated in the maintenance of the stem cell state of embryonic stem (ES) cells and induced pluripotent stem (IPS) cells. In this review, we have generated a unifying model of the action of Nm23-H1 in AML, including previously unpublished data from our laboratory, and provide arguments as to why we consider this role to be distinct from that in ES and IPS cells.