In acute heart failure with pulmonary edema, rest is a useful adjunct to pharmacologic treatment because it increases urinary flow and enhances the effectiveness of diuretic drugs. In chronic heart failure, however, there is increasing evidence that avoiding exercise can lead to deconditioning changes in skeletal muscle and in the peripheral circulation that may actually impair exercise tolerance. Exercise training was introduced as part of postinfarction rehabilitation in the 1960s, but it was not tested in patients with heart failure until well into the 1980s. Several reports have now shown considerable improvements in exercise capacity after physical training in patients with stable chronic nonedematous heart failure. Many of the peripheral abnormalities described in chronic heart failure have been shown to be at least partially reversible after physical training. These include abnormalities of skeletal muscle, respiratory gas exchange and autonomic nervous control of the circulation. Controversy still exists as to whether training may have beneficial prognostic effects in chronic heart failure and how soon after myocardial infarction it is safe to commence training. In addition, little information exists as to the most appropriate form of exercise therapy and the proper criteria for patient selection into training programs. Exercise training seems set to become a popular and beneficial adjunct to the management of patients with chronic heart failure. It has been shown to have a beneficial effect on symptoms, exercise performance and a host of pathophysiologic changes characteristic of chronic heart failure. Whether it improves prognosis is not known.