In this study of 5,505 children 11 to 12 years of age, the relationship between physical activity and blood pressure was investigated. Total physical activity was measured by accelerometer and recorded as average counts per minute. Minutes per day spent in moderate to vigorous physical activity (MVPA) were also measured. After adjustment for age and gender, the regression coefficient between total physical activity and systolic blood pressure was -0.44 (95% CI, -0.59 to -0.28) and the regression coefficient between MVPA and systolic blood pressure was -0.66 (-0.92, -0.39), suggesting that the volume of physical activity may be more important than intensity in predicting blood pressure. Given the tracking of blood pressure from childhood to adulthood, these results emphasize the importance of encouraging physical activity early in life to possibly prevent the development of hypertension in adults.