Structural alterations of the arterial wall precede atherosclerosis and cardiovascular events. Endothelial dysfunction appears to be the earliest marker for this structural change that makes the vasculature sensitive to the adverse effects of pressure, lipids, diabetes, smoking and other so-called risk factors. Reduced arterial compliance or elasticity provides an index to the structural abnormalities associated with aging and disease states. Preliminary studies suggest that an alteration in pulsewave oscillations induced at small artery branch points serves as a guide to endothelial dysfunction and reduced nitric oxide bioactivity. Additional studies are urgently needed to document the usefulness of clinical measurement of arterial compliance as a marker for the vascular abnormality that leads to cardiovascular disease and as a guide to efficacy of therapeutic interventions.