In order to search for antineoplastic components from plants, cytotoxic activity against human carcinoma cell lines was measured in 266 extracts from 236 plants using the MTT (3-[4,5-dimethyl thiazol-2-yl]-2,5-diphenyl tetrazolium bromide) method. As a result, the root of Pulsatilla chinensis (Ranunculaceae), which has been used as an insecticide in oriental medicine, showed a cytotoxic effect. Its structure was determined to be a mixture of ¥a-sitosterol-3-O-glucoside and stigmasterol-3-O-glucoside (3:1). Its IC value was 26¥ig/ml against SNU-I stomach cancer cell line.