Dyspnea is a main feature of symptomatology in asthma, and its perception does not necessarily correlates well with airway obstruction. The aim of this study was twofold: (1) to identify factors determining the subjective degree of dyspnea in patients with different grades of stable bronchial asthma and (2) to compare various clinical methods existing for grading dyspnea. The investigation comprised 153 outpatients with stable asthma. The parameters studied were the following: demographic characteristic of subjects, baseline dyspnea score by means of three clinical instruments (baseline dyspnea index [BDI], Medical Research Council [MRC] scale, and modified Borg scale), asthma severity, standard measures of physiologic lung function, anxiety, depression, subconscious illness attention, and asthma-related quality of life (HRQOL). The dyspnea scores were all significantly interrelated (r=0.77-0.85, p<0.001). The three clinical scales for grading dyspnea were significantly correlated with the same parameters: airflow obstruction, lung hyperinflation, emotional factors, HRQOL, age, age at asthma onset, asthma duration, female gender, clinical severity, and lower economical, and educational levels. Multiple regression analysis showed that independent factors determining clinical dyspnea scores were: age, airway obstruction, and emotional status. Moreover, in patients with severe asthma, lung hyperinflation helped to explain the individual dyspnea score. These data suggest that clinical methods are appropriate for evaluating the impact of dyspnea on daily activities of asthmatic patients. BDI, MRC, and Borg clinical dyspnea scales showed similarly information in subjects with asthma. Independently of asthma severity, older age, airway obstruction, and psychological disturbance were associated with higher degree of dyspnea. However, if subjects had severe airway obstruction, lung hyperinflation was a major determinant of baseline dyspnea score.