Eleven adult patients with exercise-induced asthma (EIA) were subjected to swimming and bicycle exercise under controlled conditions regarding temperature and relative humidity of the inhaled air, the respiratory frequency, tidal volume, minute ventilation and the accumulated ventilation. Swimming for 6 min was performed on the first day, and the next day the patients performed bicycle exercise. On both days the temperature of the inhaled air was 23% C and the relative humidity 15%. The average accumulated ventilation for the 6 min of exercise was 404 l for bicycle exercise and 419 l for swimming. The decrease in pulmonary function was 31% after bicycle exercise and 30% after swimming. It is concluded that the stimuli for EIA are equally effective whether exercise is performed in the form of swimming or bicycling.