Abstract: The cardiotonic glycoside (named tupistrin) was isolated from the roots of Tupistra fimbriata, Liliaceae, collected in Yunnan. Tupistrin produced a systolic stop of frog's heart in situ, and exhibited a digitalislike action on mammanian hearts in situ or perfused isolated hearts. In small doses it showed inotropic and chronotropic effects, but in toxic doses it induced arrhythmia and stopped systole. Tupistrin induced also similar ECG changes as digitalis preparation did on cats and guinea pigs. It caused vomiting in cats and pigeons at toxic dosages. On comparing its biological activity with other cardiac glycosides, the minimal lethal dose of tupistrin in pigeons was 1.394±0.069 mg per kg, while those of g-strophanthin and thevetin were 0.170±0.004mg per kg and 1.574±0.048 nag per kg respectively.