Platycodi Radix, the root of Platycodon grandiflorum, commonly known as Doraji, is used as a traditional oriental medicine. Extracts from the roots of P grandiflorum have been reported to have wide ranging health benefits. In the present study, we investigated the effects of an aqueous extract from the roots of P. grandiflorum (AEPG) on the growth of human lung carcinoma A549 cells. Upon treatment with AEPG, a concentration-dependent inhibition of cell growth was observed and cells developed many of the hallmark features of apoptosis, including condensation of chromatin. Flow cytometry analysis confirmed that AEPG increased populations of apoptotic-sub Gl phase. Immunoblot and quantitative RT-PCR analyses indicated that the expressions of Bcl-2 was down-regulated but Bax was up-regulated in AEPG-treated A549 cells. The expression of active form of caspase-3 by AEPG treatment was markedly increased, and the levels of poly(ADP-ribose) polymerase (PARP) and $eta$-catenin, its target proteins, were decreased in a concentration dependent manner. Taken together, these findings suggest that P. grandiflorum has strong potential for development as an agent for prevention against human lung cancer.