One hundred five patients with varying degrees of aortic regurgitation in either NYHA Functional Class I or II have been evaluated and are being followed prospectively in order to assess the natural history of this disease. Admission studies included echocardiography, rest and exercise radionuclide angiography, measurement of pulmonary artery wedge pressure during exercise, and 24-hour ambulatory monitoring. These studies should allow us to identify more sensitive indicators of impending clinical deterioration than are presently available.