The aim of the study was to investigate the role of serum C-reactive protein (CRP) level as a risk factor in predicting metabolic syndrome (MS), hypertension, atherogenic dyslipidemia, type 2 diabetes mellitus, and coronary heart disease. We prospectively evaluated 1270 men and 1320 women, aged 30 to 89 years, who had serum CRP determinations and a mean 4.3 years' follow-up. The CRP values were log-transformed for calculations. Metabolic syndrome was defined by the Adult Treatment Panel III criteria modified for male abdominal obesity. Prediction of outcome was performed by excluding from analysis the particular outcome variable existing at baseline examination. Smoking men had higher age-adjusted estimated CRP concentrations (P < .001), whereas smoking women had lower CRP (P = .027) than never smokers. Risk of developing an elevated (> or =2 mg/L) CRP was predicted significantly by baseline CRP in both sexes and by apolipoprotein (apo B), current smoking, and family income in men, when adjusted for 5 further variables. Baseline CRP levels predicted atherogenic dyslipidemia when adjusted for age, baseline dyslipidemia values, and apo B tertiles and predicted incident hypertension independent of age, waist circumference, and smoking status. After adjustment for sex, age, and the 5 MS components, CRP predicted newly developing MS, with a hazard ratio (HR) of 1.16 (95% confidence interval, 1.02-1.32). When adjusted for sex, age, baseline glucose, waist circumference, and apo B tertiles, diabetes was significantly predicted by CRP in women (HR, 1.31) alone. Sex- and age-adjusted CRP level identified also those that progressed to diabetes independent of a fasting glucose >100 mg/dL (HR, 1.39; 95% confidence interval, 1.21-1.59), although not in men. In the prediction of incident coronary heart disease, CRP contributed to 7 established risk factors including waist circumference with a significant 1.18-fold HR. C-reactive protein is both an independent significant predictor and a risk factor of cardiometabolic risk among Turkish adults, additive to MS components, whereby risk is modulated by sex, smoking habit, and apo B.