The medical history is the first step in the clinical evaluation of exertional dyspnea. It should include pertinent questions about the characteristics of dyspnea, especially descriptive qualities, onset, frequency, severity, and activities that provoke the symptom. Based on this information, along with the physical examination, the health care provider should be able to categorize the cause of exertional dyspnea as suspected cardiac disease, suspected respiratory disease, or as unexplained. Laboratory testing is ordered using a logical approach to diagnose the most probable cause of dyspnea. Cardiopulmonary exercise testing is indicated to differentiate cardiac and respiratory limitation, to document deconditioning, and to identify psychogenic dyspnea. The measurement of dyspnea and leg discomfort during exercise testing can be performed using the Borg 0 to 10 category-ratio scale or the visual analog scale. These perceptual responses can provide useful information about symptom limitation, which is complementary to physiologic data.