BackgroundArterial stiffness is an important determinant of pulse pressure, and of left ventricular load and coronary perfusion pressure.Assessments of stiffnessPrecise quantification is elusive, since stiffness is different in different arteries and even in the same artery at different pressures. Proximal elastic arteries and peripheral muscular arteries respond differently to aging change and to drugs. Various other terms are used to express stiffness, such as distensibility and compliance. Various indirect indices are also used, including pulse wave velocity, characteristic impedance and augmentation index.Increases in stiffnessWhile the literature is confusing, it is well established that stiffness of central arteries increases with aging and with elevated blood pressure. Effects of other diseases and of vasoactive agents are less clear-cut.