Molecular sensing by gastrointestinal (GI) cells plays a crucial role in the control of multiple fundamental functions including digestion, regulation of caloric intake, pancreatic insulin secretion, and metabolism, as well as protection from ingested harmful drugs and toxins. These processes are likely to be mediated by the initiation of humoral and/or neural pathways through the activation of endocrine cells. However, the initial recognition events and mechanism(s) involved are still largely unknown. This article reviews the current evidence that the chemosensory machinery discovered in specialized neuroepithelial taste receptor cells of the lingual epithelium is operational in enteroendocrine open GI cells that sense the chemical composition of the luminal contents of the gut.