20 patients with acute myocardial infarction and a medical history of less than six hours were treated with immediate percutaneous transluminal coronary angioplasty. The median time from start of symptoms until establishment of reperfusion of the infarct related artery was 190 minutes, and the time from admission to insertion of the balloon was 52 minutes. Angioplasty was successful in all patients, with no serious complications. All patients experienced pain relief immediately after angioplasty. No patients died or had further infarctions. None needed hospitalization during the first three months of follow up. Eight patients had an exercise test between five and seven days after angioplasty and the other 12 at their six-week check up; there were no signs of ischemia or anginal pain. Measurement of global ejection fraction one week and six weeks after treatment showed median normal values and no significant changes (58% versus 57%). Myocardial perfusion imaging was carried out in eight patients both before hospital discharge and six weeks later. Normalization and improvement was seen in six patients using this method, whereas the perfusion was found unaltered in two patients. Hibernation or stunning, or both are suggested as possible explanations for this. We found the method highly effective and safe in selected patients.