Left ventricular diastolic filling can be determined reliably by Doppler-derived mitral and pulmonary venous flow velocities. Diastolic filling abnormalities are broadly classified at their extremes to impaired relaxation and restrictive physiology with many patterns in between. An impaired relaxation pattern identifies patients with early stages of heart disease, and appropriate therapy may avert progression and functional disability. Pseudonormalization is a transitional phase between abnormal relaxation and restrictive physiology and signifies increased filling pressure and decreased compliance. In this phase, reducing preload, optimizing afterload, and treating the underlying disease are clinically helpful. A restrictive physiology pattern identifies advanced, usually symptomatic disease with a poor prognosis. Therapeutic intervention is directed toward normalizing loading conditions and improving the restrictive filling pattern, although this may not be feasible in certain heart diseases. Finally, many patients have left ventricular filling patterns that appear indeterminate or mixed. In these cases, clinical information, left atrial and left ventricular size, pulmonary venous flow velocity, and alteration of preload help assess diastolic function and estimate diastolic filling pressures.