Seven patients with acute anterior myocardial infarction were treated with a betablocker (Pindolol 0.1-0.2 mg i.v.). The goal of the study was to determine the course of the ischemic ST elevation by means of precordial Ecg mapping (sigma-ST). Within 20 min a reduction of of sigma-ST of 23% p less than 0.05 and of the heart rate of 10% p less than 0.05 was noticed. The mean arterial pressure remained constant. In one case the heart rate rose, so did the sigma-ST. -Beside heart rate reduction a competitive effect of the betablocker against myocardial catecholamines in the ischemic area may lead to these results.