Myc proteins control several cellular processes, including proliferation and growth, and they play an important role in human tumorigenesis. Several years ago, single homologs of Myc, its interaction partner Max, and its antagonist Mnt were identified in Drosophila melanogaster. Here, we review the function of this so-called Max network in fruit flies, with a particular emphasis on its most obvious biological activity: the control of cellular and organismal growth. We describe the molecular basis for this growth function, as well as the interaction of Myc with other pathways known to control growth, the insulin, TOR, and hippo pathways. In addition, Drosophila Myc also controls DNA replication and influences apoptosis, both cell-autonomously and non-autonomously, in a process known as cell competition. In the future, we expect that further functions of Myc will be uncovered and that genetic approaches will increasingly be used to characterize the evolutionarily conserved molecular mechanism of Myc action, thus also benefitting our understanding of Myc biology in vertebrates.