Exercise-induced asthma is defined as bronchospasm within the distal airways initiated by exercise. Whether the larynx responds to produce an exacerbation or alleviation of symptoms during an attack has never been evaluated. Thirty subjects were tested, including 15 normals and 15 with exercise-induced asthma. Laryngeal response to exercise was determined by measuring the area of the glottic aperture before, during, and after exercise. The glottis was visualized with a flexible laryngoscope and video images were recorded during monitoring of respirations. Asthma was induced in subjects by having them exercise on an ergometer for 10 minutes while breathing dry air at 10 degrees C. Measurements were subsequently made from recorded images and relative glottic areas were compared between groups. Our data quantify the normal physiologic response of the larynx to exercise and demonstrate a substantial laryngeal contribution to asthma induced by exercise.