Atherosclerotic coronary disease develops over several decades and was once thought to be an inevitable, irreversible consequence of aging. Atherogenesis is an inflammatory response that occurs after injury to the endothelium. Thrombosis, because of either endothelial erosion or plaque disruption, precipitates acute coronary events. Effective lipid lowering with statins has consistently and significantly decreased the risk that acute ischemic events will occur. The beneficial effects of statins likely result not only from their lipid-lowering effects but also from mechanisms that influence plaque behavior. Atherosclerotic plaques are not immutable; rather, their structure and composition can be altered by therapeutic modification. Ample evidence from clinical trials supports statin treatment in patients with stable coronary disease. Results of recent clinical trials support early treatment of high-risk patients with unstable coronary disease; early and aggressive statin treatment resulted in fewer recurrent ischemic events in patients with an acute coronary syndrome. Additional studies are needed to confirm the benefit of early statin treatment in patients with unstable coronary disease and to elucidate the reasons for the occurrence of events in treated patients. Research is also necessary to clarify the role of other lipids, as well as nonlipid risk factors, in the occurrence of acute ischemic events.