Eight new sesquiterpene lactones (chlorajapolides A-E, 1-5, chlorajaposide, 6, chlorajaponol, 7, and chloraeudolide, 8) were isolated from an ethyl acetate-soluble partition of the ethanol extract of the whole plants of Chloranthus japonicus. The structures and relative configurations of 1-8 were established on the basis of spectroscopic data analysis. All isolates obtained were evaluated for their cytotoxic activity against a small panel of cancer cell lines.