Nitric oxide (NO) plays a key role in mediating macrophage cytotoxicity towards different targets, including tumoral cells and intracellular pathogens. However, its role in macrophage immunoregulation is less well defined. In this study, we have investigated the effect of altering NO levels on the production by mouse macrophages of cytokines, and reactive oxygen intermediates as measured by luminol-dependent chemiluminescence. Our results demonstrate that NO can enhance the release of both tumor necrosis factor-alpha and interleukin-1 alpha, and chemiluminescence. Thus, in addition to acting as a powerful effector molecule in mediating cytotoxic activities of mouse macrophages, NO can play a role in enhancing the production of a variety of other inflammatory mediators, and thus can contribute both directly and indirectly to the immunopathology of macrophage-dependent inflammation.