One hundred and 10 normal subjects were studied by pulsed Doppler velocimetry to determine the range of values of blood velocity across the cardiac valves and in the great vessels. Modal peak velocities of 1.55 m/s occurred in the left heart, but right heart peak velocities were lower. In most sites a statistically significant inverse relation between peak velocities and age or body surface area was found. Time to peak velcocity in the pulmonary artery and ascending aorta increased significantly with age and was shorter in the aorta than in the pulmonary artery. These data were developed to serve as standards for the assessment of values recorded in patients with congenital and acquired cardiac disease.