The incidence and prevalence of heart failure are increasing as the population ages. Epidemiologic studies demonstrate that more than half of heart failure patients have a normal ejection fraction. The pathophysiology of this disorder is not completely understood. It is primarily attributed to left ventricular diastolic dysfunction (a leftward- and upward-shifted end-diastolic pressure-volume relation), where left ventricular diastolic chamber size is normal or reduced despite greater-than-normal filling pressures, resulting in reduced stroke volume and cardiac output. Using classic measures derived from pressure-volume analysis, we delineate other possible combinations of the end-systolic and end-diastolic pressure-volume relation, and hence possible pathophysiologic mechanisms that could underlie the syndrome of heart failure with normal ejection fraction. We propose an algorithm for identifying the primary pathophysiologic mechanism of heart failure in the setting of a normal ejection fraction using three simple factors: blood pressure, electrocardiographic/echocardiographic evidence of left ventricular hypertrophy, and left ventricular size. The application of this algorithm may aid in guiding management and targeting much-needed therapies for this population.