Diastole is the part of the cardiac cycle starting at aortic valve closure and ending at mitral valve closure. Evaluation of diastolic function by echocardiography is useful to diagnose heart failure with preserved ejection fraction, and regardless of ejection fraction, echocardiography can be used to estimate left ventricular filling pressure. Assessment of diastolic function includes analysis of left ventricular relaxation and compliance, left atrial and left ventricular filling pressures. This chapter describes the phases of diastole and covers the integrated approach of LV diastolic function through M-Mode and 2D/3D echocardiography, pulsed-wave Doppler echocardiography, and pulsed-wave tissue Doppler echocardiography.