PURPOSE: to analyze in an objective and subjective manner the voice of patients with spasmodic dysphonia in the moments before and after botulinum toxin A. METHOD: the vocal emissions of eleven women patients were recorded before and after (15 days) treatment. The vocal samples were analyzed by two experienced speech therapists through the perceptual analysis (GRBASI scale) and spectrographic analysis. RESULTS: in the perceptual analysis with subtended vowel, the altered parameters were degree of severity, strain and instability, while in connected speech only degree of severity and strain changed after treatment. In the perceptual analysis with sustained vowel, the parameters that have changed, were the degree of severity, strain and instability, while in connected speech only degree of severity and strain changed after treatment. The spectrographic analysis was improved after treatment with no statistical significance found among the parameters. CONCLUSION: there was significant improvement of the vocal analysis after treatment and, therefore, injections of botulinum toxin A were effective in the treatment of spasmodic dysphonia in this group.