Abdominal fat, in particular intra-abdominal visceral adipose tissue, is considered to be the most dyslipidemic and atherogenic fat depot in the human body. Intra-abdominal visceral adipose tissue and total body fat can be measured precisely and reliably in a laboratory setting using advanced imaging techniques; however, reliable clinical measurements of pediatric intra-abdominal visceral adipose tissue and total body fat are yet to be developed. Thus, the specific aims of this study are to 1) identify reliable landmarks and methodology for the measurement of pediatric waist circumference that are associated with intra-abdominal visceral adipose tissue and total body fat across the pediatric age, total body adiposity, and maturity range among African American and Caucasian children and adolescents, 2) determine if waist circumference in combination with other anthropometric indices is a better predictor of intra-abdominal visceral adipose tissue and total body fat than waist circumference alone across the pediatric age, total body adiposity, and maturation range, and 3) develop and determine the clinical utility of pediatric race-sex-specific waist circumference thresholds for the identification of elevated chronic disease risk factors across the pediatric age, total body adiposity, and maturation range. The investigators will accomplish these aims by conducting a cross-sectional study of 100 African American boys, 100 Caucasian boys, 100 African American girls, and 100 Caucasian girls 5 to 18 years of age. Waist circumference will be measured at the four common anatomic sites used in pediatric research: 1) superior border of the iliac crest, 2) midpoint between the iliac crest and the lowest rib, 3) umbilicus, and 4) minimal waist. Additional body dimensions will be obtained in order to determine the clinical utility of combining waist circumference with other measurements in predicting intra-abdominal visceral adipose tissue and total body fat, which will be assessed using advanced imaging techniques. The identification of the most appropriate waist circumference landmarks and measurement techniques is important for the clinical identification of children at elevated obesity-related health risk and for the standardization of obesity surveillance strategies within and between countries.