Assessment of functional capacity of patients with heart failure by means of exercise tests has recently become a new field of investigation for this diagnostic technique, constituting an incursion into an area so far out of its domains. It has been demonstrated that the functional capacity of these patients has a diagnostic and prognostic value, in addition to being the most accurate method to evaluate therapeutic effects. In patients with valvular disease, the performance of an exercise test, especially if other techniques are simultaneously being used, both invasive (catheterization) and non-invasive (respiratory parameters, isotopic angiography), yields very precise information, as regards for instance the determination of the correct timing for surgical repair, as well as prognostic information in some situations, such as aortic insufficiency.