OBJECTIVE To compare anti-tumor activities of different extracts from the medicinal plants Pinellia ternata and its allied species in vitro.METHODS FCM assays were used to detect cell apoptosis.And cell cycle,Caspase-3 expression of better extracts were analyzed.RESULTS The main active components were the ethyl acetate extracts or the parts of total organic acid.Among them,Rhizoma Pinelliae and Rhizoma Pinellia Pedatisectae were activer than Rhizoma Typhonii Flagelliforme.A further experiment concerning extracts from Rhizoma Penillia Pedatisectae,showed that the anti-tumor effects of these herbs were related to cell cycle arrest in S phase and Caspase-3 induced apoptosis.CONCLUSION Rhizoma Pinelliae,Rhizoma Pinellia Pedatisectae and Rhizoma Typhonii Flagelliforme all have anti-tumor activities.But Rhizoma Penillia Pedatisectae may be more effective.And inducing cell apoptosis was one of their mechanisms of action.