Little attention has been directed to the utility of unsupervised physical training at home in postmyocardial infarction patients. The present investigation was designed to assess the effects of exercise training at home on functional parameters soon after myocardial infarction. One hundred and eighteen male postmyocardial infarction patients under 70 years old, that performed a predischarge exercise test, were randomly allocated soon after the acute event, into a 12-14 weeks unsupervised physical training at home and into a control group. The control group patients were informally encouraged to practice exercise. Before training, the cardiorespiratory parameters were similar in both groups. After training, improvement of all these variables was seen in both groups, although the magnitude was greater in the training group. Maximal oxygen consumption increased 7.6 +/- 3.6 ml/kg/min in the training group by 3.8 +/- 2.6 ml/kg/min in the control group (p = 0.00001), maximal heart rate increased 14.6 +/- 13.4 by 8.4 +/- 5.7 beats/min (p = 0.001), and similar results were obtained with maximal double product and exercise test duration (33 +/- 46 versus 17 +/- 12, p = 0.009; 2.2 +/- 1.1 versus 0.9 +/- 1.1 min, p = 0.00001) always in trained patients favour. Nine trained patients and 16 control patients showed myocardial ischemia in both exercise tests. At ischemic threshold, the achieved improvement was again greater in trained patients, concerning to heart rate (p = 0.02), double product (p = 0.0005) and exercise time (p = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)