Initial research established the feasibility of exercise training in patients with heart failure, as well as associated physiological benefits. This review summarizes the findings from over two dozen single-site studies that address the effect of exercise training on exercise capacity and cardiovascular and peripheral function. In addition, it incorporates the results from two meta-analyses and a recently completed multi-center trial, all of which studied the effects of exercise training on clinical outcomes. The major conclusions from these studies are that exercise training is safe; improves health status and exercise capacity; helps attenuate much of the abnormal pathophysiology that develops with heart failure; and yields a modest reduction in clinical events. The magnitude of the clinical benefits appears related to the volume of exercise completed. Future research is needed to identify which patient subgroups might benefit the most from exercise training, the optimal exercise dose or load needed to lessen disease-related symptoms and maximize clinical benefit, and the effects of exercise training in patients with heart failure and preserved left ventricular systolic function.