Diastolic dysfunction of the heart is characterized by normal left ventricular contractility and normal ejection fraction, however ventricular relaxation is impaired. In systolic dysfunction, ventricular contractility and ejection fraction are reduced, in addition to impaired relaxation. The prevalence of diastolic dysfunction is increased in the elderly, especially those who have had inadequately treated hypertension. Both diastolic and systolic dysfunction may result in similar clinical signs and symptoms. Therefore, echocardiography is needed to make the distinction. Left atrial (LA) enlargement, assessed by left atrial volume indexed to body surface area, appears to be the best measure to assess diastolic function. LA enlargement is likely when indexed LA volume is > or = 34-40 mL/m2. B-type natriuretic protein appears to be useful for the diagnosis, assessment and prognosis of heart failure, but it does not distinguish between the two types of dysfunctions. Several drug treatments that have effects on the mechanism of diastolic dysfunction are under investigation.