—Human cytomegalovirus (CMV) infection of smooth muscle cells generates reactive oxygen species (ROS) and thereby activates nuclear factor κB (NFκB), which causes expression of viral and cellular genes involved in immune and inflammatory responses. These changes could account for the mounting evidence suggesting that CMV may contribute causally to restenosis and atherosclerosis. We found that CMV induces ROS, at least partly, through a cyclooxygenase-2 (COX-2)–dependent pathway. Moreover, the viral immediate-early (IE) gene products, IE72 and IE84, have the capacity to transactivate the COX-2 promoter. Aspirin and indomethacin, both cyclooxygenase inhibitors as well as direct ROS scavengers, reduce CMV-induced ROS, probably through both of these activities. Sodium salicylate also has antiviral effects as the result of its potent antioxidant properties. Furthermore, by reducing ROS, aspirin and sodium salicylate inhibit CMV-induced NFκB activation, the ability of IE72 to transactivate its promoter, CMV IE gene expression after infection of SMCs, and CMV replication in SMCs. This is the first time aspirin has been shown to have antiviral effects. Thus, it is possible that aspirin has previously unrecognized therapeutic effects in various clinical situations, such as in viral infections (when used as an antipyretic agent) and in atherosclerosis (when used as an antiplatelet agent).