Exercise has been shown to be an important component of pulmonary rehabilitation and may be associated with both physiologic and psychological benefits for patients with chronic lung disease. In evaluating patients for pulmonary rehabilitation, exercise testing can be useful in measuring exercise tolerance, assessing causes of exercise limitation, developing a prescription for training, evaluating often unexpected changes in arterial blood gases, and screening for exercise-induced bronchospasm. A variety of testing procedures and measurements are available in pulmonary laboratories. The appropriate test depends on several variables, including patient and program goals, questions identified in the initial patient evaluation, the specific exercise training program, available laboratory expertise, and cost.