Acute Lymphoblastic Leukaemia (ALL) is the most common neoplasm in children but the mechanisms underlying leukemogenesis along with the dynamics of leukemic cell proliferation are poorly understood. The importance in understanding the proliferation dynamics of leukaemia lies in the fact that our knowledge from the point of first appearance to the moment of clinical presentation, we know almost nothing. Further on, describing cell proliferation dynamics in a more mature, probably mathematical, way it could lead us to the understanding of disease ontogenesis and thus its aetion. This chapter reviews the current knowledge on proliferation dynamics and proliferation non-linear dynamics of the leukemic cell. Furthermore, we present some “in-house” experimental data that support the view that it is possible to model leukemic cell proliferation and explain how this has been performed in in vitro experiments.