We performed this study to understand the molecular basis underlying the antitumor effects of Saussurea lappa, Pharbitis nil, Plantago asiatica and Taraxacum mongolicum, which have been used for herbal medicinal treatments against cancers in East Asia. We analyzed the effects of these medicinal herbs on proliferation and on expression of cell growth/apoptosis related molecules, with using an AGS gastric cancer cell line. The treatments of Saussurea lappa and Pharbitis nil dramatically reduced cell viabilities in a dose and time-dependent manner, but Plantago asiatica and Taraxacum mongolicum didn't. FACS analysis and Annexin V staining assay also showed that both Saussurea lappa and Pharbitis nil induce apoptotic cell death of AGS. Expression analyses via RT-PCR and Western blots revealed that Saussurea lappa, but not Pharbitis nil, increased expression of the p53 and its downstream effector p21^Waf1, and that the both increased expression of apoptosis related Bax and cleavage of active caspase-3 protein. We also confirmed the translocation of Bax to mitochondria. Collectively, our data demonstrate that Saussurea lappa and Pharbitis nil induce growth inhibition and apoptosis of human gastric cancer cells, and these effects are correlated with down- and up-regulation of growth-regulating apoptotic and tumor suppressor genes, respectively.