Subcostal echocardiography of the left ventricle was continuously recorded during balloon dilatation of the aortic valve in ten consecutive elderly patients. Left ventricular wall motion decreased gradually during a minute of maintained complete balloon inflation. Blind analysis of M mode echocardiograms showed a significant reduction in fractional shortening. Deflation of the balloon resulted in global left ventricular hyperkinesia. There was a transient overshoot in fractional shortening, wall thickness, and blood pressure approximately 40 s after deflation of the balloon. The myocardial reaction was similar to that known to occur regionally with brief coronary artery obstruction, whereas the timing of the events seemed to be dissociated from the timing of changes in left ventricular load. Thus it is likely that the left ventricular response during valve dilatation reflects not only changes in load but also an ischaemia-reperfusion effect on the myocardium. The systolic thickening of the hypertrophied interventricular septum was slightly reduced after balloon dilatation. This finding might be a result of repeated episodes of ischaemia and reperfusion. However, the potential for myocardial injury seemed to be unimportant clinically.