Objective To describe the effects of exercise training on chronotropic incompetence in patients with stable heart failure, as measured by their inability to achieve a peak exercise heart rate greater than 85% of maximum. Background Exercise intolerance and chronotropic incompetence are characteristic of patients with heart failure. Exercise training improves exercise capacity in these patients; however, to what extent reversal of chronotropic incompetence contributes to such a response remains uncertain. Methods Fifty-one patients undergoing standard medical therapy were randomly assigned to a 24-week exercise training program or a no exercise control group. Twenty-one of 26 patients assigned to the exercise group and 22 of 25 control patients completed the study. Peak oxygen consumption, resting and exercise plasma norepinephrine level, and quality of life (Living With Heart Failure Questionnaire) were assessed. Results A significant (P < .05) increase in peak heart rate was observed in the exercise group (9 ± 3 beats/min) when compared with the control group (1 ± 3 beats/min). Among exercise-trained patients with chronotropic incompetence at baseline (n = 14), the increase in peak heart rate at week 24 was 12 ± 3 beats/min. Peak oxygen consumption was significantly (P < .05) increased in the exercise group (204 ± 57 mL/min) versus the control group (72 ± 33 mL/min). Health-related quality of life was not significantly changed with exercise training. Twenty-four weeks of exercise training induced a greater (P < .05) reduction in plasma norepinephrine at rest and during exercise in patients with a nonischemic cardiomyopathy versus those with ischemic cardiomyopathy. Conclusions Exercise training results in an increase in peak heart rate and partial reversal of chronotropic incompetence among patients with stable heart failure. These responses contribute, in part, to the exercise training–induced increase in exercise capacity that occurs in these patients. (Am Heart J 1999;138:233-40.)