The physical, metabolic and psychological advantages of cardiac rehabilitation and its effects on secondary prevention and mortality are discussed. The importance of functional assessment of the patient with postacute myocardial infarction (MI) is emphasized in order to define the prognostic and therapeutic approaches. The methods of assessment are described, ith particular regard to Echocardiography, ambulatory ECG and exercise test. The echocardiographic location and extension of left ventricular asynergy, which are often unpredictable with conventional ECG, have important functional implications. In our experience, on the basis of these data, subsets of patients with different degrees of left ventricular dysfunction, both at rest and during exercise, can be identified. The ambulatory ECG can reveal ventricular arrhythmias in 60% of infarcted patients, while during exercise test the incidence of ventricular premature beats (VPB) is 20%. Both in post-acute evaluations and in evaluations performed 1 year later, poor correlations were found between VPB and ECGraphic and hemodynamic parameters either at rest or during exercise; however during the first postinfarction year ventricular arrhythmias tend to decrease. Hemodynamic and ECGraphic patterns during exercise were analyzed in about 600 patients with recent MI: the left ventricular filling pressure (PWP) was greater than 20 mm Hg in 54% of the patients and greater than 30 mm Hg in 28%. The MI site is predictive of hemodynamic left ventricular dysfunction both at rest and during exercise: anterior MIs are more impaired than inferior MIs. Good correlations were found between the ST-segment elevation (increased ST) during exercise and left ventricular function; in particular, in anterior MI the ventricular function is generally normal in patients without increased ST, abnormal in those with increased ST (the increased ST increment during exercise, if present at rest, has no hemodynamic implications). In inferior MI the increased ST does not seem to have nay hemodynamic significance. The ST-segment depression (decreased ST) too, is of important functional significance: in anterior MI it is usually associated with increased ST and a more evident left ventricular dysfunction. In inferior MI, ventricular function is generally better in patients without decreased ST than in those with increased ST.(ABSTRACT TRUNCATED AT 400 WORDS)