In this report we have investigated the effects of BAX in enhancing apoptosis in two primary non-small cell lung cancer cell lines. A count of the apoptotic cells by TUNEL staining revealed that almost 70% of BAX over-expressing cells died, while very few apoptotic cells were detectable in the wildtype cells or in the cells transfected with an empty vector. These findings suggest that de-regulated expression of BAX may provide a novel mechanism for initiating cell death in non-small cell lung cancer cells. Further studies are needed to better define the involvement of this protein in the complex mechanism of lung carcinogenesis and to definitely demonstrate the therapeutic utility of targeting this pathway.