Forty asymptomatic patients were studied after a first uncomplicated myocardial infarction. They were 36 men and 4 women, with a mean age of 52.6 yr; the location of myocardial infarction was in the anterior wall in 18 (45%) patients and in the inferior wall in 22 (55%). The patients were submitted to: (1) 48-h Holter monitoring, during the 2nd and 8th weeks after the acute event; (2) exercise testing during the same periods; (3) cardiac catheterization and coronary arteriography. Patients with clinical conditions associated with cardiac rhythm disturbances or repolarization abnormalities were excluded. The electrocardiographic methods identified 11 (27.5%) patients with silent myocardial ischemia. Patients with and without silent ischemia were similar in relation to sex, age, coronary risk factors, arrhythmias, left ventricular function and follow-up. Patients with silent ischemia had more inferior wall myocardial infarctions, but the difference was not statistically significant. Patients with silent ischemia had significantly more extensive coronary artery disease (45.5% multivessel disease) when compared to those without ischemia (14.8% multivessel disease) (p < 0.05). After a 2-yr follow-up, 4 (36.4%) patients with and 1 (3.4%) without silent ischemia had a coronary event (p < 0.05). Kaplan-Meier analysis demonstrated a significantly higher cumulative probability of not experiencing a new coronary event for the patients without silent ischemia (96.5%) as compared to those with silent ischemia (62.3%) (p < 0.01). Our results suggest that silent myocardial ischemia after a first uncomplicated myocardial infarction carries an adverse prognosis and should be routinely investigated.