Four new alkaloids, tuberostemonone [1], tuberostemonol [2], stemoamide [3], and tuberostemospironine [4], together with two known alkaloids, tuberostemonine and didehydro tuberostemonine, were isolated from the roots of Stemona tuberosa (Stemonaceae). Their structures were elucidated by it, ms, and ID- and 2D-nmr techniques including difference nOe spectra and homonuclear and heteronuclear spectral analyses. © 1992, American Chemical Society. All rights reserved.