Approximately 50% of patients with a firm clinical diagnosis of heart failure (HF) have a normal ejection fraction. Some patients have valvular disease, but most have underlying diastolic dysfunction that leads to pulmonary and systemic congestion and signs and symptoms of HF. Although diastolic HF is clinically and radiographically indistinguishable from HF with depressed left systolic ventricular function, knowledge of which patients are at risk of diastolic HF, the common clinical profiles, and the common echocardiographic findings enhances the clinician's ability to diagnose diastolic HF with confidence. The prognostic implications of a diagnosis of diastolic HF and the therapeutic approach to such patients are reviewed.