Inflammation participates critically in atherosclerosis. Circulating levels of several inflammatory markers rise in individuals at risk for atherosclerotic events. In particular, elevation of plasma C-reactive protein (CRP), a nonspecific acute-phase reactant that is easily and reliably measured, has strong predictive power for cardiovascular events. Indeed, measurements of high-sensitivity CRP (hs-CRP) plasma levels add to both the prognostic information gleaned from assay of plasma lipid risk factors and the risk levels estimated by means of Framingham study-based criteria. Retrospective data suggest the hypothesis that hs-CRP plasma levels may be useful for guiding use of lipid-lowering therapy in individuals who appear to be at low risk according to traditional risk assessment. A large-scale, randomized clinical trial-Justification for the Use of Statins in Primary Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER)-will test whether rosuvastatin therapy will reduce incident cardiovascular disease in subjects with elevated plasma hs-CRP concentrations who do not meet current criteria for initiation of lipid-lowering drug therapy. Such clinical trial data may provide an evidence base for the use of plasma CRP assay as an adjuvant guide to therapy to complement the established traditional risk factors such as plasma lipid levels. Thus, medical practitioners are ushering in an era in which the biology of inflammation in atherosclerosis will find its way into clinical application.