Five new stemoninine-type alkaloids, bisdehydrostemoninine ( 1), isobisdehydrostemoninine ( 2), bisdehydroneostemoninine ( 3), and bisdehydrostemoninines A ( 4) and B ( 5), were isolated from the crude-alkaloid extract of the roots of Stemona tuberosa. Their structures were elucidated on the basis of one- and two-dimensional NMR and other spectroscopic studies. The relative configuration of 4 was determined by X-ray diffraction. Alkaloid 1 displayed significant antitussive activity in the citric acid-induced guinea pig cough model.