In 18 patients with coronary artery disease and in 12 control subjects, left ventricular function was studied by means of rapid artial pacing. The results were compared with the cardiac dynamics, as determined by left ventricular dysfunction although the angiograms portrayed normal contractility at rest. It has to be assumed, that abnormal myocardial function was only evident during the pacing stress. On the other hand, if the angiogram showed local hypokinesis, the hemodynamic effect of this slightly abnormal contraction could be determined by atrial pacing. Moreover, rapid atrial pacing often produced myocardial ischemia and anginal pain in patients with coronary heart disease. In these cases the transient "anginal" depression of left ventricular function could be separated from the chronic hypoxic "preanginal" dysfunction. This may be of vale in terms of surgical revascularisation.