Progress in the development of surgical techniques for the treatment of aortic stenosis has provided a new challenge to physicians.1-4 The increasing number of patients undergoing aortic valve surgery is a clear indication that management of patients with this lesion includes the evaluation and selection of candidates for surgical intervention.5-8 Experience in other forms of operable heart disease has shown that the proper selection of patients for surgery depends on the fulfillment of three requirements: (1) that the descriptive aspects and life history of the disease be well established; (2) that the pathologic physiology of the lesion be known; (3) that a quantitative estimate of severity can be made, either clinically or with the aid of special techniques. The first requirement is abundantly fulfilled by the many excellent studies dealing with the clinical aspects and clinicopathologic correlations in aortic stenosis.9-12 Most of these studies, however, were not