Pulmonary exercise testing is intended to evaluate the functional capacity of a patient and to identify the limiting factors. Its indications cover the whole spectrum of the diseases associated with dyspnea. Many clinical situations can easily be resolved during a non-invasive test merely by measuring ventilation, heart rate and systemic blood pressure. For the determination of pulmonary gas exchange, samples of arterial blood and expiratory O2 and CO2 fractions are necessary. In comparison with other pulmonary function tests, exercise testing is the only technique which provides overall information on the many adaptive mechanisms triggered by exercise. Consequently, it is of special value in distinguishing between pathophysiological states.