Two new sesquiterpenes, named carpabrotalactone A (1) and B (2), together with six known sesquiterpenes, 11 (13)-dehydroivaxillin (3), eriolin (4), 2 alpha,5 alpha- dihydroxy-11 alpha H-eudesma-4(15)- en-12,8 beta- olide (5), (5 alpha)-5-hy-droxyasperilin (6), 1 alpha,4 alpha-dihydroxy-guaia-11(13)-ene-12,8 alpha-olide (7) and 4 alpha,5 alpha-dihydroxy-guaia-11(13)-en-12,8 alpha-lactone (8), were isolated from the herbs of Carpesium abrotanoides L. The structures of these sesquiterpenes were elucidated based on spectroscopic analysis, and single crystal X-ray diffraction analysis. All the compounds exhibited potent cytotoxicity against the ISK, Hela, A549, Sw620, RBE and Caco-2 cell lines, with IC50 values ranging from 7.8-47.4 mu M. In addition, compounds 2, 3, 4, 7 and 8 displayed significant anti-influenza A (H1N1) virus activity with IC50, values of 6.2, 11.6, 16.4, 1.3 and 0.4 mu M, respectively.