Recent studies have revealed the clinical usefulness of central blood pressure (BP) as an index of risk for cardiovascular disease. The arterial pulse waveform is the sum of the forward pressure wave generated by left ventricular ejection and a backward propagating wave that is subsequently reflected from the peripheral site, and the time point at which these forward and backward propagating waves merge and the amplitude of the reflected (backward) wave affect the level of central BP. The augmentation index (AIx) has been proposed as a measure of the wave reflection, and its clinical usefulness has also been evaluated. In the process, the non-linear relationship between age and AIx, the prognostic value of AIx, and the various effects of antihypertensive drugs on AIx have been shown. However, the clinical usefulness of AIx has not been established, and several questions about its use remain. Future studies will be needed to address these questions, and may contribute to important changes in the management of cardiovascular disease. In this review, we present recent findings on the AIx and discuss the role of this parameter in clinical practice.