The aim of this study was to investigate the cytotoxic effect and its mechanism on Radix Aconiti(RA) extract in lung cancer cell lines. RA extract treatment decreased the cell viability in a dose-dependent fashions in lung cancer cells including A549, H460, H23 and H157 cells. Many investigators reported that A549 and H460 cells expressed wild-type p53, but H23 and H157 cells preserved mutated p53. After treatment with RA extract in A549 and H460 cells, we measured the expression of p53 protein levels using Western blot. analysis. In both cells treated with RA extracts, p53 protein expressions were increased in a dose-dependent manner. In our experiments, RA extracts also have cytotoxic effects in H23 and H157, which have mutated p53. Treatment with RA extract decreased bcl-2 protein expressions in both cells. These results suggest that RA extracts have cytotoxic effects via p53 expression increase and bcl-2 inhibitable pathways in A549, H460 cells and H23, H157 cells, respectively.