Four new alkaloids, didehydrotuberostemonine A (1), stemoninone (2), tuberostemospiroline (3), and tuberostemonine L (4), together with seven known alkaloids, were isolated from the roots of Stemona tuberosa. Their structures were elucidated on the basis of spectroscopic analysis. The known alkaloids were identified as 2-oxostenine (5), tuberostemonine (6), sessilifoliamide H (7), tuberostemonone (8), didehydrotuberostemonine (9), bisdehydrostemoninine (10), and tuberostemoamide (11). © 2009 Verlag Helvetica Chimica Acta AG.