On the basis of evaluating bronchial lability, when performing exercise tolerance test and salbutamol inhalation in 111 school age children suffering from bronchial asthma, it has been shown that the index of bronchial lability (IBL) and the index of bronchospasm (IBS) may be used as a specific accessory test in corroborating a severe (uncontrolled) course. The use of the given parameters to verify mild (controlled) bronchial asthma is inexpedient because of a high rate of obtaining false results.