Defects in the asymmetric division of stem/progenitor cells can lead to an imbalance in the generation of self-renewing vs differentiating daughter cells, one of the early events which may lead to malignant transformation.Studies on Drosophila neural stem cells, neuroblasts, one of the better models for understanding asymmetric divisions, have revealed that several cell cycle regulators also play important roles in mediating neuroblast asymmetric divisions, and this connection may explain the tumour suppressor property of some of these molecules.In this talk I will summarise recent findings from my lab which reveal how key cell cycle regulators can impinge on the machinery which control neuroblast asymmetry to mediate asymmetric protein localisation and/or the decision to self-renew or differentiate---and conversely, how key components of asymmetric division can affect the decision of whether or to what extent progenitor cells can undergo self-renewal.