An increased airway responsiveness to inhaled nonspecific stimuli has been often observed in cystic fibrosis patients. But bronchial hyperreactivity in such patients is due, in most cases, to damaged bronchial mucosa rather than to coexistent asthma, and it remains under question whether or not bronchodilators are of help in cystic fibrosis. Indeed some authors reported adverse effects after inhalation of beta-mimetic drugs. This behavior seems to be due to an "instability" of the bronchial walls in cystic fibrosis. Nevertheless other studies showed that bronchodilators could be of help when administered in some cases and during definite periods in the evolution of the disease. Indeed, variability in responsiveness to bronchodilator drugs is one of the features of cystic fibrosis and therapy must be adjusted to this variability in every patient. In any way, pulmonary functional tests must be performed before and after administration of a bronchodilator drug and before beginning such therapy.