The pumping function of the left ventricle depends both on its ability to empty and its capacity to fill at a low pressure. Diastolic dysfunction occurs when filling of the left ventricle necessary to produce an adequate cardiac output requires an elevated pulmonary venous pressure. Diastolic dysfunction can be secondary to systolic dysfunction or occur with normal systolic function (primary diastolic dysfunction). Primary diastolic dysfunction most commonly results from systolic hypertension, left ventricular hypertrophy, and aging. Primary diastolic dysfunction is an important cause of heart failure, especially in elderly patients. Diastolic dysfunction can be recognized from the pattern of mitral valve flow velocity measured by Doppler echocardiography. Strategies to improve diastolic function include: control of systolic blood pressure, preservation of sinus rhythm, and avoidance of tachycardia.