Seven adolescent patients with bronchial asthma performed bicycle exercise tests on several occasions, within 1 week. After the determination of baseline pulmonary function (using spirometry, maximal expiratory flow-volume curves and body plethysmography), all subjects were exercised on the bicycle ergometer for 10 min. On each occasion a different level of minute ventilation (VE, 1/min) was achieved, because of different work performed. Following each exercise test, the degree of exercise-induced bronchoconstriction was assessed. It was found that the degree of bronchoconstriction, as measured by pulmonary function tests, is function of VE measured during exercise. A dose-response-like relationship, i.e., level of VE vs. bronchoconstrictive response, seems to be an important individual characteristic of the airway reactivity of young patients with bronchial asthma.