METHODS Diagnostic bronchoscopy performed on untreated African patients with tuberculosis revealed alveolar macrophages filled with carbon particles. It was postulated that this was the result of excessive inhalation of smoke from domestic fires and the consequent phagocytosis by alveolar macrophages. OBJECTIVE To determine whether carbon particles influence the release of superoxide and hydrogen peroxide radicals by the alveolar macrophage during killing of Mycobacterium bovis. METHODS Alveolar macrophages were recovered by bronchoalveolar lavage from adult rabbits and cultured. Experimental macrophages were exposed to M. bovis and carbon particles, controls only to M. bovis. Superoxide release was measured by the superoxide dependent cytochrome C reduction method and hydrogen peroxide release by luminol dependent chemiluminescence. Significance of differences was calculated by Student's t-test for unpaired data. RESULTS For superoxide and hydrogen peroxide release, results show a significant difference between the experiments and the controls. Hydrogen peroxide radicals are, however, released at a low constant average median value in the controls. CONCLUSIONS Hydrogen peroxide is not greatly involved in the killing of M. bovis by alveolar macrophages since low concentrations are released in the controls. Ingestion of large amounts of carbon particles decreases the release of superoxide and hydrogen peroxide radicals.