Abstract-Aortic stiffness, peripheral wave reflection, and aorta-to-peripheral pulse pressure amplification all predict cardiovascular risk. However, the pathophysiological mechanism behind it is unknown. Tonometric pressure waveforms were recorded on the radial, carotid, and femoral arteries in 138 hypertensive patients (age: 56Ϯ13 years) to estimate aorta-to-peripheral amplifications, aortic augmentation index, and aortic (carotid-femoral) pulse wave velocity. The femoral Doppler velocity waveform was recorded to calculate the reverse/forward flow index and diastolic/systolic forward flow ratio. The aorta-to-femoral and aorta-to-radial amplifications correlated inversely with the aortic augmentation index and pulse wave velocity. The femoral flow waveform was triphasic, composed of systolic forward, subsequent reverse, and diastolic forward phases in 129 patients, whereas it was biphasic and lacked a diastolic forward flow in 9 patients. Both the femoral reverse index (30Ϯ10%) and diastolic forward ratio (12Ϯ4%) correlated positively with the aorta-to-femoral amplification and inversely with the aortic augmentation index and pulse wave velocity; these correlations were independent of age, sex, diastolic pressure, and femoral artery diameter. Patients with biphasic (versus triphasic) flow were older, shorter, included more diabetics, had smaller femoral diameters, and showed greater aortic pulse wave velocity even when adjusted for all of these covariates. In conclusion, because of the inverse (peripheral-to-aortic) pressure gradient, pulse pressure amplification normally produces a substantial reversal of the femoral flow, the degree of which is determined by the aortic distensibility and peripheral wave reflection. Arteriosclerosis (increased stiffness, increased augmentation, and reduced amplification) decreases both the reverse and diastolic forward flows, potentially causing circulatory disturbance of truncal organs and lower extremities. Key Words: blood pressure Ⅲ blood flow Ⅲ arteriosclerosis Ⅲ aorta Ⅲ physiology Ⅲ femoral Ⅲ wave reflection T he arterial pulse provides important information on the cardiovascular prognosis. There is substantial evidence that the aortic pulse wave velocity (PWV) and augmentation index (AIx) predict cardiovascular morbidity and mortality in a variety of populations, as confirmed by recent meta-analysis studies. 1,2 Similar prognostic significance has been also demonstrated for pulse pressure amplification from the central aorta to peripheral medium-sized muscular arteries. [3][4][5] These pulse indices (PWV, AIx, and pulse amplification) depend on the structural and functional properties of the central elastic and peripheral muscular arteries, which interact closely through pressure wave transmission and reflection. 6 -9 Potential mechanisms mediating these pulse abnormalities and cardiovascular disease progression include elevated central pressure leading to an increase in cardiac afterload 10,11 and widened pulsatile pressure causing circumferential tensile stress that...