Symptoms of myocardial ischemia occur in aortic stenosis in the absence of coronary artery disease. Increased left ventricular wall tension, a principal determinant of myocardial oxygen requirements, may contribute to these symptoms. This investigation was undertaken during the course of transseptal left heart catheterization in order to study the effect of nitroglycerin on left ventricular wall tension in eight patients with fixed orifice aortic stenosis. In seven of the subjects, nitroglycerin significantly reduced tension-time index per beat and per minute. In addition, left ventricular size may have diminished as a consequence of lower diastolic filling pressure. In view of the relationship between wall tension and myocardial oxygen consumption, these effects should favorably influence the balance between oxygen availability and oxygen requirements in patients with fixed obstruction to left ventricular outflow. The eighth patient experienced an appreciable increase in tension-time index, suggesting secondary hypertrophic subaortic stenosis.