Hemodynamic data obtained during rest and exercise in 22 patients with aortic stenosis were analyzed. Mean aortic valve gradient for the group did not change significantly during exercise but there was large individual variability. Aortic valve flow increased during exercise in all but 2 patients. There was no correlation between change in gradient and change in flow during exercise. Although the mean calculated aortic valve area for the group did not change significantly during exercise, the calculated area was larger during exercise in most patients. Change in the calculated valve area correlated best with changes in aortic valve flow, left ventricular stroke work index, and the product of left ventricular systolic pressure and stroke volume. This suggests that in some patients there may be a dynamic component to aortic valve obstruction that may vary with changing hemodynamics.