Background and Methods Inflammation plays an important role in the initiation and progression of atherosclerosis and in the pathogenesis of acute cardiovascular events. Recent studies have indicated a possible association between C-reactive protein (CRP) and the clinical outcome of coronary artery disease (CAD). We studied prospectively in a group of 125 patients with premature CAD whether plasma levels of CRP as measured with a high-sensitivity assay predict risk for future coronary events. All patients had stable CAD at time of blood sampling but had originally been seen with unstable angina or myocardial infarction. The mean follow-up time after blood collection was 54 months, and death, myocardial infarction, need for coronary revascularization, or admission to hospital with angina pectoris were defined as clinical end points. Results Patients in the highest tertile of CRP levels had a >3.8-fold risk (risk ratio 3.82, 95% CI 1.19-12.17) for death, myocardial infarction, or need for coronary revascularization compared with the patients in the first tertile. The relative risk for patients in the second tertile was 3.5-fold higher (95% CI 1.04-11.56). CRP levels in the third tertile independently predicted risk after adjustment for lipids and other clinical risk factors. Conclusion In patients with clinically stable conditions who have a positive history for acute coronary syndromes before age 50 years, plasma levels of CRP higher than 1.6 mg/L are predictors of future coronary events and therefore indicate the role of underlying chronic inflammation for the clinical course of CAD. Accordingly, reference limits for prediction of risk in CAD have to be lower in this specific patient group than in middle-aged or elderly patients. (Am Heart J 2002;144:449-55.)