Left ventricular assist devices (LVAD) are used increasingly as bridges to cardiac transplantation. The typical LVAD candidate is a bedridden, critically ill, New York Heart Association (NYHA) Class IV patient with congestive heart failure (CHF) who is dependent upon intravenous, inotropic, and, in many cases, intra-aortic balloon support. The LVAD provides the potential for pre transplant rehabilitation by allowing the patient to become ambulatory, and by improving muscle tone, muscle mass, and nutritional status before transplantation. However, whether the abnormal exercise capacity of these patients improves after implantation has not been elucidated. The purpose of the present study was to evaluate the exercise capacity of patients with CHF after LVAD implantation (n = 10) using peak oxygen consumption during maximal exercise (MVO2), and comparing the results with those of a group of NYHA Class III patients with CHF (n = 14). After 2 months of implantation, MVO2 of the patients with LVAD was 12.8 +/- 0.3 ml/kg/min, which was comparable to that of the NYHA Class III patients with CHF (12.5 +/- 0.5 ml/kg/min). Four of 10 patients with LVAD were monitored for more than 5 months when MVO2 rose to 15.4 +/- 1.0 ml/kg/min (p < 0.05 vs NYHA Class III). In conclusion, the exercise capacity of patients with LVAD recovers slowly but significantly after 5 months of implantation, promising the potential for complete recovery from heart failure in patients supported with an LVAD.