Inhibitory effects of extracts from fruits and fruit juices of Citrus unshiu Marc. (Unshiumikan) encapsulated in hybrid liposomes (HL) composed of L-alpha-dimyristoylphosphatidylcholine (DMPC) and polyoxyethylene(20) sorbitan monooleate (Tween 80) on the growth of tumor cells were examined in vitro. The extracts with lower polar solvents significantly inhibited the growth of human hepatoma (HuH-7) cells and human stomach cancer (MKN-45) cells, though the extracts with higher polar solvents showed no or little antitumor activity. These results suggest that hydrophobic antitumor compounds are present in fruits and fruit juices of Unshiumikan.