To evaluate the toxic effects of various oxidants on alveolar macrophages (O2, NO2, tobacco smoke and silica), we used an original method of cell culture in aerobiosis, which permitted direct contact between the atmosphere and the target cells. Our results demonstrated that the variations of cell sensitivity to the cytotoxic effects of oxidants were associated with various levels in cellular antioxidant equipment. A significant correlation was found between cytotoxicity and antioxidant enzymes (superoxide dismutase and catalase) and/or cellular glutathione. Addition of N-acetylcysteine, a polypeptide known to have an antioxidant activity and to be a precursor of glutathione, was responsible for a decrease of oxidant-mediated cytotoxicity. Whether this protective effect was due to an increase in glutathione cell content or to a scavenger effect of N-acetylcysteine still needs to be elucidated.