Eight compounds were isolated from the stems of Brucea mollis by various chromatographic techniques such as column chromatography on silica gel and Sephadex LH-20, and preparative HPLC, and their structures were elucidated as bruceolline O (1), 1-(1-beta-glucopyranosyl)-1H-indole-3-carbaldehyde (2), canthin-6-one (3), 11-hydroxycanthin-6-one (4), 9-methoxycanthin-6-one (5), 4-methoxycanthin-6-one (6), infractin (7), and beta-carboline-1-propionic acid (8). The cytotoxic activities of compounds 1-8 against HCT-8 and A549 human cell lines were determined, but none of them exhibited significant activity (IC 50 > 10 micromol x L(-1)). Among them, compound 1 is a new indole alkaloid, and compounds 2 and 5-7 were isolated from this plant for the first time.