Three new xanthanolides, 1-3, along with nine known compounds, were isolated from the aerial parts of Carpesium longifolium. The structures of the new compounds were elucidated as 1beta,4beta-epoxy-5beta-hydroxy-10alphaH-xantha-11(13)-en-12,8beta-olide (1), 1beta,4beta,4alpha,5beta-diepoxy-10alphaH,11alphaH-xantha-12,8beta-olide (2), and 4-acetoxy-1beta,5beta-epoxy-10alphaH-xantha-11(13)-en-12,8beta-olide (3) by spectroscopic methods including IR, EIMS, HRESIMS, and 1D and 2D NMR experiments. Parthenolide and michelenolide exhibited significant cytotoxic activity against cultured SMMC-7721 (human hepatoma) and HO-8910 (human ovarian carcinoma) cells.