Diverse biological and developmental functions are mediated by signalling through the epidermal growth factor (EGF) receptor. lit flies, many different mechanisms are used to control and restrict EGF-R signalling, including ligand processing, ligand variety (an inhibitor as well as activators), transcription and perhaps subcellular localization of the receptor. Since the components of EGF-R signalling have been well conserved, understanding these different modes of receptor regulation in flies should lead to general insights into the strategies of receptor activation.