This study aimed to reveal the relationships among C-reactive protein (CRP), obesity, blood pressure (BP), and serum lipids in children. Eighty-six obese and 58 non-obese boys aged an average of 11.2 years were examined. Serum CRP levels were measured by high sensitivity latex turbidimetric immunoassay and subjects with CRP levels below 0.3 mg/dl were adopted. Comparisons of serum CRP levels, BP, and serum lipids levels between age-matched obese and non-obese groups were performed. A comparison of serum CRP levels among the percentage of relative weight quartiles and the relationships among percentage of relative weight, BP, and serum lipids in CRP quartiles were analyzed. The relationships between CRP and other parameters were analyzed by simple and stepwise multiple regressions. Obese children had significantly higher high-sensitivity CRP (hs-CRP) levels than their non-obese counterparts. The mean hs-CRP level was 5.5-fold higher in the top quartile of the percentage of relative weight than in the bottom quartile. In the top quartile of CRP, the percentage of relative weight, systolic BP, diastolic BP, pulse pressure, and low density/high density lipoprotein-cholesterol (LDL-C/HDL-C) were significantly higher than in the bottom quartile. The percentage of relative weight, BP, LDL-C, and apolipoprotein B (ApoB) showed positive correlations and HDL-C showed a negative correlation with log CRP by simple regression. Stepwise multiple regression analysis indicated that only the percentage of relative weight was strongly related to CRP. In conclusion, this study revealed a significant relationship between CRP and obesity in children. Obese children tended to have high CRP levels, BP elevation, and slight dyslipidemia. These results support the findings that CRP is one of the useful indices of childhood obesity that would affect the progression to future atherosclerotic disease. We consider that a strategy of preventing obesity from childhood would contribute to a drop in the future incidence of metabolic syndromes. (Hypertens Res 2003; 26: 541-546)