OBJECTIVE: To examinie the synergistic effects of Banxia Xiexin Decoction (, Known as Banhasasim-tang in Korean) extract (BXDE) on cisplatin-induced cytotoxicity in the A549 human lung cancer cell lines. METHODS: A549 cells were treated with varying concentrations (50-200 μg/mL) of cisplatin and BXDE alone or in combination for 96 h. We used 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan assay and flow cytometry to analyze cell viability and apoptosis, respectively. RESULTS: The exposure of cells to cisplatin and BXDE alone or in combination decreased cell viability dose- and time-dependently (P<0.05), which was found to be mediated by the apoptotic pathway as confirmed by the increase in the annexin V/propidium iodide- stained cell population and a ladder pattern of discontinuous DNA fragments. Furthermore, the apoptosis was inhibited by the pan-caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethylketone (z-VAD-FMK). CONCLUSIONS: BXDE significantly potentiated apoptotic effects of cisplatin in A549 cells. Moreover, apoptosis induced by BXDE might be the pivotal mechanism mediating its chemopreventative action against cancer.