Recent epidemiological studies have shown that arterial stiffness, measured through carotid-femoral pulse wave velocity (PWV), has an independent predictive value for cardiovascular (CV) events in several populations, including patients with uncomplicated essential hypertension1,2 and type 2 diabetes.3 Arterial stiffness is thus an intermediate end point for CV events, predicting CV events independently of and beyond peripheral pulse pressure (PP). Peripheral PP, central PP, and augmentation index, which provide additional information on wave reflection, are considered “surrogates” of arterial stiffness, because their pathophysiological meaning is clearly different.4–6 Central PP and augmentation index are dependent on the speed of wave travel, the amplitude of reflected wave, the reflectance point, and the duration and pattern of ventricular ejection, especially with respect to change in heart rate and ventricular contractility. Aortic PWV, which is the speed of wave travel, represents intrinsically arterial stiffness, according to the Bramwell-Hill formula.4–6 Two articles7,8 in the present issue of Hypertension raise the issue of the predictive value of “surrogates of arterial stiffness” for CV events. Li et al7 studied the dynamic relationship between diastolic blood pressure (DBP0 and systolic blood pressure (SBP) in ambulatory blood pressure monitoring (ABPM) data throughout the day and calculated a novel index as 1− the regression slope of DBP on SBP. This index was named ambulatory arterial stiffness index (AASI) on the basis that “average distending BP …