Taste receptors have been defined at the molecular level in the past decade， and cell-based assays have been developed using cultured cells heterologously expressing these receptors. The most popular approach to detecting the cellular response to a tastant is to measure changes in intracellular Ca(2+) concentration using Ca(2+)-sensitive fluorescent dyes. However， this method cannot be applied to food-derived samples that contain fluorescent substances. To establish an assay system that would be applicable to fluorescent samples， we tested the use of Ca(2+)-sensitive photoproteins， such as aequorin and mitochondrial clytin-II， as Ca(2+) indicators in a human sweet taste receptor assay. Using these systems， we successfully detected receptor activation in response to sweetener， even when fluorescent compounds coexisted. This luminescence-based assay will be a powerful tool to objectively evaluate the sweetness of food-derived samples even at an industry level.