The subcellular distribution of the epidermal growth factor receptor and its interaction with second messenger proteins has been explored using tagging with green fluorescent protein and its derivatives. EGFR itself has been fused with GFP and its natural life cycle and its internalisation in response to ligand determined. Several second messenger proteins including Shc and PI3kinase have also been tagged with fluorescent proteins and their subcellular redistribution in response to ligand activation has been filmed. The physical interaction of the EGFR with second messengers has been studied by FRET and other proximity assays. These systems will not only reveal much about the behaviour of the system in live cells but may also be useful for observing the effects of signal transduction inhibitor drugs such as antibodies and small molecule tyrosine kinase inhibitors. Finally, they have the potential to be developed into screens for new compounds which affect the system.