Two new taxoids, taxumairol Q (1) and 13-O-acetyl wallifoliol (2), have been isolated from the leaves and twigs of Taxus sumatrana. Taxuspine F and wallifoliol (10) have been isolated for the first time from the yew T. sumatrana. Seventeen known taxoid diterpenoids have also been isolated. The new derivatives, 9,13-diacetyltaxumairol W (3), 10,13-dibenzoyltaxacustin (4), 7,13-diacetylwallifoliol (5), 7,13-dibenzoylwallifoliol (6), and 7,9-dibenzoyltaxumairol P (7), have been prepared by acylation of a crude mixture of taxoids. All structures were established primarily on the basis of 1D and 2D NMR techniques, including DEPT, COSY, and HMBC experiments, as well as chemical correlation with known compounds. Wallifoliol (10) exhibited significant cytotoxicities against both Hepa 59 T/VGH (human liver carcinoma) and KB (human oral epidermoid carcinoma) tumor cells. Taxuspine F and compound 5 possessed moderate activity against Hepa cells only, while 3, 6, 7, and 10-deacetylbaccatin III showed only marginal activity against Hepa cells.