Ethnobotanical studies have been of very great importance in recognizing plants that contain substances that modulate the heterodimer T1R2-T1R3 sweet taste receptor, inclusive of Stevia rebaudiana (Asteraceae) and Siraitia grosvenorii (Cucurbitaceae).In addition to reviewing relevant ethnobotanical literature, inclusive of original field work conducted, the authors have provided a progress report on the ultimate regulatory acceptance of highly sweet ent-kaurane (steviol) diterpene glycosides from S. rebaudiana leaves ("stevia") and cucurbitane triterpene glycosides (mogrosides) from the fruits of S. grosvenorii (popularly known as "monk fruit"). Despite their relatively high prices relative to that of sucrose, the steviol glycosides and mogrosides are of current great interest for further more extensive utilization on the market as sweet-tasting non-caloric food additives, due to increases in the rates of obesity and diabetes all over the world. Recent phytochemical work on the sweet principles of these two species is highlighted, including the important "next-generation" sweetener, rebaudioside M, from S. rebaudiana.Initial observations on the ethnobotany of both S. rebaudiana and S. grosvenorii have proved crucial to indicating the presence of their sweet-tasting principles to the wider scientific community.Ethnobotanical observations have been pivotal in enabling the discovery of many sweet-tasting plant constituents, with those of S. rebaudiana and S. grosvenorii both being examples. Extractives prepared from these species are now commercially used widely in the U.S. as additives for the sweetening of foods and beverages.