Methods to test airway responsiveness to inhaled agonists in children were originally developed for use in adults, and agonist dosage regimens do not adequately correct for the size of the child. Because small children receive a higher dose relative to their body size than do large children, the age-related decline in airway responsiveness reported in many recent studies might reflect failure to adequately size-correct test dosages rather than a genuine physiological event. Until the administered doses of inhaled agonists can be satisfactorily size-corrected, tests of airway responsiveness in children should be regarded as qualitative rather than quantitative.