We investigated the relationship between the clustering of risk factors for metabolic syndrome and the plasma C-reactive protein (CRP) concentration as measured by high-sensitive CRP assay. Body mass index, waist circumference, triglycerides (TGs), high-density lipoprotein cholesterol, fasting glucose, systolic and diastolic blood pressures, insulin, and CRP were measured in 1046 Korean adults (560 males; age, 18-64 years) in 2003 to 2004. There were statistically significant positive correlations for log CRP with body mass index, waist circumference, log TG, log insulin, and log homeostasis model assessment in both sexes after adjusting for age and smoking status. High-density lipoprotein cholesterol showed a significant negative correlation with log CRP in both sexes. For both sexes, the mean level of log CRP increased with increasing number of risk factors of metabolic syndrome (P for trend <.01 for males and <.001 for females). Stepwise multivariate linear regression analysis showed that waist circumference contributed the largest portion of the variance in CRP levels in both sexes. Log homeostasis model assessment and log TG were independently associated with log CRP levels only in females. These results indicate that CRP, a marker of inflammation that underlies atherosclerosis, is associated with the clustering of each metabolic syndrome risk factor and, furthermore, that abdominal obesity is the strongest predictor of CRP level in the Korean adult population.