Two naturally occurring new sesquiterpene ketones, neoacolamone (1) and 7α-hydroxyneoacolamone (2), were isolated from the roots of Chloranthus serratus (Thunb.) Roem. et Schult. (Japanese name: Futari-shizuka, Chloranthaceae). The structures were elucidated on the basis of their physicochemical properties and chemical reactions. Three sesquiterpene ketones, acoragermacrone (3), acolamone (4) and zederone (5), and four additional sesquiterpenes including lindenanolides were also found in the same source. The relationships of these isolates to the constituents of C. japonicus and to the sesquiterpene biogenesis in the Chloranthus species are discussed.