A growing body of literature has underscored the value of ventilatory gas exchange techniques during exercise testing (commonly termed cardiopulmonary exercise testing) and their applications in the management of patients with cardiovascular and pulmonary disease. Once limited to the domain of research physiologists and pulmonary medicine, the test is now widely used in clinical practice; guidelines on exercise testing from major organizations list specific indications for the use of cardiopulmonary exercise testing. The added precision provided by this technology is useful in terms of quantifying the response to therapy, evaluating disability, assessing the mechanism of exercise intolerance, making activity recommendations to patients, and quantifying the response to training. Importantly, a significant body of data published in recent years has documented the prognostic utility of cardiopulmonary exercise testing. A cardiopulmonary exercise test can supplement other clinical and exercise test information when precision is important, when the patient's symptoms are mixed, or when it is unclear why the patient was referred for exercise testing. Information from the test can also be used to support the important recommendation that the patient engage in an exercise program.