The coronary arteriography and left ventriculography were performed on 63 patients with acute myocardial infarction who were admitted to coronary care unit of Seoul National University Hospital from September 1984 to October 1986 within 30 days after onset of acute myocardial infarction (median: 16 days) to delineate the extent of coronary artery disease and the left ventricular function. The results were as follows; 1) The ratio of male to female was 59:4 (14.75:1) and 34.9% of all patients were at their 6th decade. 2) The infarction were transmural in 58 patients (92.1%) and nontransmural in 5 patients (7.9%). Among 58 patients with transmural infarction, 33 (56.9%) had anterior wall infarction, 15 (25.9%) had inferior wall infarction and 10 (17.2%) had anteroinferior wall infarction. 3) Among 63 patients, 4 (6.3%) showed completely normal coronary artery on coronary arteriography and 3 (4.8%) had insignificant stenosis (lesser than 50%) reduction in luminal diameter). The 39.7% of all patients had one-vessel disease, 27% two-vessel disease and 22.2% three-vessel disease. 4) Among 58 patients with transmural infarction, 31 (53.4%) showed complete occlusion of infarct related artery. And 73.4% of the patients with inferior wall infarction showed complete occlusion of infarct related artery. None of the patients with non-transmural infarction had complete occlusion. 5) In 21 patients who had the coronary arteriography within 14 days after the onset, 12 (57.2%) showed complete occlusion of infarct related artery and among 42 patients who were studied 15-30 days after the onset, 19(45.2%) showed complete occlusion. 6) Nineteen patients (30.2%) were found to have left ventricular aneurysm. 7) The left ventricular ejection fraction were significantly higher in the patients with non-transmural infarction than in patients with transmural infarction. The difference in left ventricular ejection fraction between the patients with anterior infarction and with inferior infarction, between single vessel disease and multiple vessel disease were not significant. 8) The older age group showed a tendency to have higher prevalence of multivessel disease. 9) As complication of coronary arteriography and left ventriculography, one episode of ventricular fibrillation was observed without mortality. From the above results of this study, it is concluded that coronary arteriography and left ventriculography can be safely performed within 30 days after the onset of acute myocardial infarction: A significant number of patients had normal or minimally diseased coronary artery: more than half of the patients with transmural infarction had complete occlusion of infarct related artery: the patients with nontransmural infarction had better left ventricular function than with transmural infarction.