This study was undertaken to determine whether adaptations to short-term exercise training after myocardial infarction, could affect the response of heart rate, blood pressure and double product at submaximal workload, and the behavior of electrocardiographic ST segment depression. We studied 60 patients (group A) who underwent a modest level exercise training for 3 months and 40 patients (group B) who did not participate in this program. All these subjects were involved in the trial 1 week after discharge from the hospital. Submaximal treadmill stress test was performed after the 3-month period. The stress test duration was longer (p < .01), heart rate (p < .001), systolic blood pressure (p < .01) and double product (p < .01) at submaximal workload were lower and the onset of ST depression of 1 mm was delayed (p < .01) in group A. In conclusion, postinfarction short-term exercise training increases the exercise tolerance, decreases the heart rate, systolic blood pressure, and double product response to exercise and improves the ischemic threshold.