To treat the acute phase of myocardial infarction, nitroglycerin and urokinase were injected directly into the infarct-related coronary artery. Left ventricular ejection fraction and regional ejection changes were significantly preserved in the chronic phase, compared with conventional therapy in patients with obstruction at the same site. Comparing left ventricular function in the acute and chronic phases, left ventricular ejection fraction, regional ejection changes and left ventricular end-diastolic pressure were significantly improved in the chronic phase in patients with reperfusion within 6 hours. On the other hand, in patients who had no reperfusion in either the acute or chronic phase, left ventricular ejection fraction deteriorated in the chronic phase. Even in patients with reperfusion in the acute phase, reocclusion later meant a worse left ventricular ejection fraction in the chronic phase. These results suggest that intracoronary thrombolysis with urokinase within 6 hours gives a good chance of recovery from myocardial damage in patients with myocardial infarction.