Relapsing polychondritis is a disease characterized by progressive inflammation of cartilagenous structures including those of the glottis, trachea, or central bronchi. We performed detailed physiologic and radiologic studies of the respiratory tract in five patients with respiratory involvement due to relapsing polychondritis. We found that the maximal expiratory and inspiratory flow-volume loop and airway resistance together can provide useful clues as to the presence, site, and fixed or dynamic nature of the upper airway obstruction in these patients. However, in patients with fixed upper airway obstruction or compound lesions, computer tomography of the respiratory tract, cinetracheography, or laryngotracheograms at different lung volumes were required to identify the site of the obstruction and to clarify the dynamic nature of the obstruction.