Background-C-reactive protein is an emerging risk factor for cardiovascular disease. Although the relations between C-reactive protein and other risk factors for cardiovascular disease have been extensively studied in adults, the relations in children are not well understood. Methods and Results-Data from 2846 boys and girls 3 to 17 years of age who participated in the National Health and Nutrition Examination Survey, 1999 to 2000, a cross-sectional survey of the US population, were used. In univariate analyses, significant associations were observed between C-reactive protein concentration-measured with a high-sensitivity assay-and age, body mass index, systolic blood pressure, and triglyceride concentrations in both sexes. In multiple linear regression analyses, body mass index was the best predictor of C-reactive protein concentration. Age was positively associated with C-reactive protein concentration among boys 3 to 17 years of age. Some race or ethnic differences were present as well among boys 8 to 17 years of age and girls 8 to 11 years of age. Systolic blood pressure was positively associated with C-reactive protein among girls 12 to 17 years of age. Conclusions-Among the sociodemographic and cardiovascular disease risk factors, body mass index was the best predictor of C-reactive protein concentration in children.