The objective of this study was to investigate the ability of patients with stable asthma to recognize improvement in bronchial obstruction with treatment. We enrolled 75 stable asthmatics (44 women and 31 men, mean age 43 17 years) who reported baseline dyspnea on a modified Borg scale. Acute bronchodilation of 15% was provoked in the laboratory, after which the patients were asked if there was a change in dyspnea. Our results were as follows. 1) Overall, 19 asthmatics (25%) failed to perceive improvement in dyspnea with bronchodilation. 2) The mean change in dyspnea was 1.17 1.11, although the change was greater in patients with more severe asthma (0.60 0.5 for mild asthmatics, 1.05 1.07 for moderate asthmatics and 1.93 1.4 for severe asthmatics; p < 0.0001). 3) Perception of improvement was significantly related to level of the patient's emotional balance (anxiety-depression), quality of life, education, socioeconomic level, age, age of onset, severity, baseline dyspnea and obstruction, thoracic pressure and number of visits to the doctor in the preceding year. 4) The variables entered into the stepwise regression model were baseline dyspnea, depression, thoracic pressure and age. 5) Generally, young asthmatics whose disease appeared at a younger age and who also had less ventilatory obstruction and greater quality of life, showed a tendency to underestimate the beneficial effect of bronchodilator treatment. Moreover, when asthma was severe, non-perceptive individuals had significantly more admissions to intensive care units due to asthma exacerbation.In conclusion, 25% of our asthmatics are unable to recognize whether their bronchia dilate as a result of treatment, meaning that they would delay the start of rescue medication during an exacerbation. Such patients should be identified in order to establish therapeutic guidelines in function of objective home criteria (peak-flow monitoring).