Membrane proteins represent a valuable source of potential drug targets due to their intimate involvement in a wide variety of disease states, including diabetes, cancer and neurological disorders. Defining the proteome of these often rare amphipathic molecules can be accomplished by exploiting the highly accurate and sensitive nature of mass spectrometry (MS). Technical advances have enabled MS to become a valuable tool for detailed mechanistic investigations into membrane proteins of unknown and known structure. The transfer of MS-screening strategies that have already been successfully used to identify interactions between soluble proteins and potential ligands, should allow the identification of drug candidates for membrane proteins in the near future.