This invention relates to chimeric taste receptors comprising the extracellular portion of one T1R or a variant or fragment thereof, either T1R1 or T1R2, and the transmembrane portion of another T1R or a variant or fragment thereof, either T1R1 or T1R2, preferably associated with a T1R3 polypeptide and a suitable G protein. These chimeric taste receptors and cells which express such chimeric taste receptors are useful in assays for identifying sweet and umami ligands as well in assays for identifying sweet and umami enhancers. Additionally, these chimeric taste receptors and cells which express same can be used to map and determine where specific sweet and umami ligands interact with their respective receptors and to elucidate the mechanism of receptor activation.