Exercise tolerance in patients with normal cardiac function can improve with an exercise program. Controversy exists whether this is also true for patients with congestive heart failure (CHF). The limiting symptoms in patients with CHF are shortness of breath and fatigue. Hemodynamic parameters do not correlate well with exercise capacity in patients with CHF. These symptoms may be more related to factors that cause fatigue during exercise than to hemodynamic parameters or even to changes in pulmonary capillary pressure. The factors that cause symptoms include an increased lactate production and metabolic and blood flow abnormalities in the skeletal muscle. Exercise training can improve vasodilation and oxidation capacity, thereby reducing lactate production. Exercise programs may improve exercise capacity in the majority of patients with CHF due to coronary artery disease or idiopathic cardiomyopathy. However, certain patients with ischemia and with anterior infarctions may experience a detrimental effect on their cardiac function. Further studies are needed to better enable recognition of these patients but until this is possible, good clinical judgement must suffice.