Abstract-Childhood obesity is increasingly prevalent in the community and is related to adverse cardiovascular outcomes during adulthood. In this study of healthy children, we evaluated the influence of adiposity and physical activity on carotid-femoral pulse wave velocity (PWV), an index of arterial stiffness and a marker of cardiovascular risk in adults. In 573 community-based children (mean age: 10.1Ϯ0.3 years; 51% boys), we measured body mass index and waist circumference. Percentage body fat was quantitated by dual-energy x-ray absorptiometry. Cardiorespiratory fitness (CRF) and physical activity levels were assessed using a 20-m shuttle run and 7-day pedometer count, respectively. PWV was estimated by applanation tonometry. In univariate analysis, PWV was positively correlated with body mass index (rϭ0.34), waist circumference (rϭ0.32), and percentage body fat (rϭ0.32; PϽ0.001 for all) and negatively correlated with CRF (rϭϪ0.23; PϽ0.001) and pedometer count (rϭϪ0.08; Pϭ0.046). In separate multivariable linear regression models, body mass index, waist circumference, and percentage of body fat were independently and positively associated with PWV (PϽ0.01 for all) after adjusting for age, sex, systolic blood pressure, mean arterial pressure, heart rate, and CRF (PϽ0.01 for all). The influence of CRF on PWV was attenuated after adjusting for adiposity. In conclusion, increased body mass and adiposity and decreased CRF are associated with arterial stiffening in healthy prepubescent children.