Corticosteroids are one of the most important lines of treatment of ronchial asthma, but they have many systemic and local side effects, among which is dysphonia. In this study 40 asthmatic patients (20 patients were treated with steroids and 20 patients were not treated with steroids), and 20 control subjects were taken, all subjects were examined by laryngoscope, acoustic and aerodynamic studies. Examination revealed hazardous effects of steroids (especially systemic steroids) on vocal folds and subsequently on voice. It was found that the longer the duration of steroids treatment, the more hazardous the effects on the vocal folds and thereby voice production. Therefore, it is recommended to restrict dose and duration of steroid intake to the least effective level.