OBJECTIVE: To assess exercise capacity and left ventricular function using magnetic resonance imaging (MRI) among patients with chronic heart failure randomized to a residential rehabilitation programme at baseline and six years after participation. DESIGN: Randomized controlled study. SETTING: Residential cardiac rehabilitation centre and community hospital. INTERVENTION: One month of intensive exercise and risk reduction therapy including educational sessions, a low-fat diet, and 2 hours of individually prescribed exercise daily. Control subjects received usual care. Subjects were evaluated at baseline, after completing the one-month residential programme and six years later. SUBJECTS: From an original study group of 50, 16 patients (8 exercise, 8 controls) with chronic heart failure were alive and available for evaluation after six years. MAIN MEASURES: Cardiopulmonary exercise test responses and ventricular size and function using MRI. RESULTS: Peak Vo(2) was 20.0 and 12.4% higher after the rehabilitation programme and six years later, respectively, whereas minimal changes were observed among controls. Left ventricular mass and volumes tended to decrease among subjects in the exercise group, whereas left ventricular mass and volumes tended to increase among control subjects after six years. Ejection fraction increased approximately 20% in both groups. CONCLUSION: Six years after participation in a concentrated residential rehabilitation programme, exercise capacity was preserved and no significant changes were observed in ventricular size or function. These findings provide further support for exercise rehabilitation in chronic heart failure.