In patients with acute myocardial infarction a substantial reduction in mortality can be achieved by early intravenous thrombolytic therapy. The beneficial effect of thrombolysis on left ventricular function is relatively small, and it seems unlikely that this minor improvement alone can be responsible for the reduction in cardiac death. So far it has not been clearly established how thrombolytic therapy affects postinfarction myocardial ischemia. From studies evaluating ST segment changes on exercise testing or ambulatory monitoring it is concluded that thrombolysis probably results in a reduction of residual ischemia. The reduced ischemic burden is proposed to be one important pathophysiological mechanism underlying the frequently observed improvement in hemodynamic stress test variables following thrombolytic treatment.