Long-term prognosis was studied in 156 patients with acute myocardial infarction (AMI) with 1-vessel coronary artery disease (CAD). During a mean follow-up period of 110 months, 19 patients (14%) had reinfarction, 15 (9.6%) died (including 7 deaths of cardiac origin) and 15 (9.6%) were hospitalized for worsening of angina. A coronary arteriogram was obtained twice in 54 patients. The coronary arteriogram revealed multivessel CAD in all cases with reinfarction (n = 14). Ten percent of the patients with multivessel disease experienced a reinfarction during the initial 3 years after the onset of the first AMI. The recurrence rate of AMI in patients with 1-vessel disease increased gradually from the third year after the onset of their first AMI, reaching 10% in 6.7 years. The recurrence of AMI at the same region as the original infarction was detected in only 1 patient. Six of 19 patients (32%) with recurrence of AMI died and 13 survived after the reinfarction. It was difficult to predict future progression from the outcome of the comparison between the first and second coronary arteriograms. Thus, in patients with uncomplicated AMI with 1-vessel CAD, the prognosis is relatively good and the frequency of reinfarction is very low with conservative treatment.