['To explore the molecular mechanisms by which mitochondrial estrogen receptor β (ERβ) suppresses non-small cell lung cancer cell apoptosis induced by apoptotic stimulations.', 'The mitochondrial localization of ERβ in non-small cell lung cancer cell lines A549 and 201T was determined using immunofluorescence and Western blotting. The changes of apoptosis of the cells with mitochondrial ERβ overexpression or knockdown in response to cisplatin and STS treatments were assessed, and mitochondrial ERβ interaction with the pro-apoptotic protein Bad was detected using co-immunoprecipitation and Western blotting.', 'ERβ was localized in the mitochondria in A549 and 201T cells. ERβ overexpression significantly reduced while ERβ knockdown increased Bax activation and cell apoptosis induced by cisplatin and STS. Mitochondrial ERβ interaction with pro-apoptotic protein Bad may suppress Bax activation and its translocation to the mitochondria.'] Does [ Mitochondrial estrogen receptor β inhibit non-small cell lung cancer cell apoptosis via interaction with Bad ]?