AbstractRecent studies have indicated the existence of a novel regulatory system governing cell growth and differentiation. The system is based on the cellular homologues of the transforming genes (oncogenes) of retroviruses. Cellular oncogene products include regulators of the cell generation cycle, cell‐surface receptors, and growth factors. Preliminary evidence is available that this regulatory system is important in hemopoiesis. In this paper, the biology of the blast cells of acute myeloblastic leukemia is reviewed. Data is presented indicating that genetic control may be exercised in the nucleus to affect self‐renewal, at the cell surface, to mediate cell‐to‐cell interactions and through the environment by the production of growth factors. These findings support the suggestion that the blast population is a suitable model for studying oncogene‐based regulation. Blasts have the further advantage that laboratory observations made with their use can be correlated with the clinical course of th