Phytochemical investigation of the taxane diterpenes content of an acetone extract of the leaves and twigs of Taxus sumatrana (Taxaceae) has resulted in the isolation of five new taxane diterpenes esters, tasumatrols H–L (1–5) together with 13 known taxanes (11–23). Compound 5 is the first 21-carbon taxane ester to be isolated from a natural source. The structures of these taxanes as well as their derivatives were established on the basis of spectral analyses, especially MS as well as 1-and 2D NMR. Compounds 2 and 4 showed significant activity against human liver carcinoma (Hepa59T/VGH), human large cell carcinoma of the lungs (NCI), human cervical epitheloid carcinoma (Hela), human colon adenocarcinoma (DLD-1) and human medulloblastoma (Med) cell lines.