Inhibitory effects of hybrid liposomes (HL) composed of L-alpha-dimyristoylphosphatidylcholine and polyoxyethylene (20) sorbitan monolaurate including extracts from Polygonum cuspidatum on the growth of human acute lymphatic leukemia (MOLT-4) cells were examined. Inhibitory effects of HL including extract (1) with petroleum ether and extract (3) with chloroform on the growth of MOLT-4 cells were obtained. In particular, remarkably high inhibitory effects of HL including extract (3) were obtained as compared with those of HL including the other extracts. Extract (3a) isolated from extract (3) using preparative layer chromatography (PLC) was identified with emodin on the basis of IR, (1)H NMR, and melting point measurements. These results suggest that hydrophobic antitumor agents including emodin should be present in Polygonum cuspidatum.