Parameters of physical working capacity (symptom limited treadmill test with gas analysis, 6 min walk test and usual everyday activity), activity of muscular metaboreflex, efficacy of pulmonary ventilation, and heart rate variability were studied in 50 patients with postinfarction cardiosclerosis with chronic class I-III heart failure and 30 patients without heart failure. Patients with heart failure of all functional classes had lowered parameters of working capacity while metaboloreflex hyperactivation and diminished effectiveness of ventilation were found only in patients with clinical signs of chronic heart failure but not in those with symptomless left ventricular dysfunction. Therapy with metoprolol was associated with lowering of activity of metaboloreflex, augmented effectiveness of ventilation and heart rate variability, improvement of results of 6 min test and everyday activity without considerable changes of peak oxygen consumption.