Residual oil fly ash (ROFA) is a pollutant dust that stimulates production of reactive oxygen species (ROS) from mitochondria and apoptosis in alveolar macrophages (AM), but the relationship between these two processes is unclear. In this study, human AM were incubated with ROFA or vanadyl sulfate (VOSO₄), the major metal constituent in ROFA, with or without L-NAME, diphenyleneiodonium (DPI) and mitochondrial electron transport inhibitors. Interactions among production of ROS, NO and apoptosis of AM were determined. ROFA-stimulated ROS production was attenuated by DPI, rotenone, antimycin and NaN₃, but not by L-NAME, a pattern mimicked by VOSO₄. ROFA-induced apoptosis was inhibited by L-NAME and a caspase-3 like protease inhibitor, but not by mitochondrial inhibitors. ROFA enhanced NO-mediated increase in caspase-3 like activity. VOSO₄ had minor effects on apoptosis. Thus ROFA-stimulated production of ROS from mitochondria was independent of apoptosis of AM, which was mediated by activation of caspase-3 like proteases and NO. The pro-oxidant effect but not the pro-apoptotic effect of ROFA was mediated by vanadium.