Benzethonium chloride (BZN) inhibites lung cancer cell proliferation. A. A549 cells were treated with the 528 FDA-approved drugs separately, and cell viability was determined by WST-1 assay. B. BZN structure diagram. C. WST-1 assay was performed to detect cell viability in the A549 and H1299 cells treated with different concentrations of BZN for up to 72 h. D. The A549 and H1299 cells treated with BZN (up to 20 μM) were compared for colony formation ability. E. A549 and H1299 were treated with BZN (up to 20 μM) for 48 h, and apoptotic cells were detected by flow cytometry. Note that BZN significantly increased the percentage of apoptotic cells in a dose-dependent manner. F. Western blotting was performed to compare expression levels of caspase-3, cleaved caspase-3, PARP and cleaved PARP. Bars, SD; *P < 0.05; **P < 0.01; ***P < 0.001 compared with DMSO-treated cells.