Exercise testing in the late hospital phase of acute myocardial infarction (MI) should be performed for all patients without contraindications. Signs of ischemia (exertional angina and ST-segment depression), ventricular arrhythmias, and duration of exercise are important both for prognosis and clinical management. Blood pressure and heart rate response to exercise, nonischemic symptoms, and physical examination for an exercise-induced third heart sound or murmur of mitral regurgitation are of further value in prescribing post-MI therapy and exercise regimens. Reported series vary widely in selection criteria for exercise testing and in testing technique, which has resulted in different conclusions about the prognostic significance of exercise test variables. Risk for posthospital cardiac death is low in post-Mi patients who are well enough to perform the test. However, even among these low-risk patients, the exercise test identifies high-risk subgroups and suggests specific pathophysiologic mechanisms underlying the stratification of risk.