The availability of molecular probes for approximately half of the 20 known complement genes now permits a detailed examination of the regulation of complement expression in liver and at extrahepatic sites in tissue macrophages. Primary cell culture, cell lines and cells transfected with DNA bearing complement genes have been used in this analysis. Pretranslational regulation of complement production has been induced by well defined cytokines such as interleukin-1 and gamma-interferon, as well as directly by endotoxin. The effect of those agents on complement genes is tissue and species specific and is developmentally regulated. These data form the basis for the elucidation of the genomic structural requirements for regulation of inflammation and, by extension, specific immune responsiveness.