The onset of symptoms or left ventricular systolic dysfunction heralds a poor prognosis for patients with either aortic stenosis or aortic regurgitation. Echocardiography is the primary imaging modality for assessment of aortic valvular lesions. Cardiac catheterization is indicated to determine the severity of the aortic valve lesion when there is a discrepancy between the clinical findings and the results of echocardiography in patients with either symptoms or left ventricular dysfunction. For patients with low-gradient, low-output aortic stenosis, dobutamine provocation should be used to differentiate truly severe aortic stenosis from patients with a primary cardiomyopathy and low aortic valve area due to low forward flow. Aortic valve surgery improves myocardial performance by relief of ventricular afterload in both patients with severe stenosis and those with severe regurgitation. Surgery should be pursued in both patients with severe aortic stenosis and those with severe regurgitation regardless of the degree of left ventricular dysfunction.