Recent evidence indicates that phagocytic cells play a major role in tissue inflammation. The release of enzymes, lipid metabolites such as prostaglandins, and reactive oxygen species by these cells appear to mediate the inflammatory process. In this study we have evaluated the effects of diethyldithiocarbamate (DDC) on human monocyte function and metabolism. We demonstrate that DDC impairs that antibody-dependent cytoxicity (ADCC) of monocytes to red cell targets. The concentration of DDC which caused maximal suppression of ADCC also prevented the burst of oxidative metabolism in monocytes stimulated by sensitized red cells targets or phorbol myristate acetate (PMA). DDC also impairs the lipid metabolism of these cells as indicated by a decrement in malonyldialdehyde (MDA) production. These data indicate that DDC impairs the activity of two major biochemical pathways in monocytes which are related to the inflammatory process, i.e., the release of oxygen metabolites and prostaglandins.