Left ventricular pressure and volume during diastole reflect the interaction of ventricular elastic, viscous, and inertial properties, and the completeness of myocardial relazation. Myocardial relaxation may be impaired in the acutely ischemic ventricle, partly accounting for the abnormal diastolic pressure-volume relation in this condition. Altered elasticity of its wall can cause increased stiffness of the ventricular chamber, as in aortic stenosis, coronary heart disease, and infiltrative cardiomyopathies. In aortic stenosis, increased left ventricular stiffness results in an increase in pressure increment associated with left atrial contraction. Generation of such a high filling pressure is critical in maintaining adequate end diastolic sarcomere stretch in the left ventricle and probably accounts for the frequent deterioration of patients with aortic stenosis after development of atrial fibrillation or nodal rhythm. Many signs and symptoms of cardiac failure, previously attributed to impaired systolic performance, may be due to partly to altered diastolic properties of the ventricular chambers.