OBJECTIVE: To evaluate vocal acoustic measures in patients with laryngeal adductor dystonia before and after 30 days of treatment with botulinum toxin. METHODS: Vocal samples were collected from 16 individuals with laryngeal adductor dystonia. The study population comprised 11 women and 5 men, mean age 62.5 years, who had undergone unilateral treatment with botulinum toxin type A. We analyzed 10 acoustic parameters using Advanced Multi-Dimensional Voice Programme software (Kay Pentax ®). Measurements were compared using Student's t test. RESULTS: There were changes in the following phonatory parameters: F0 range semi-tones (p = 0.02), number voice break (p = 0.03), F0-tremor intensity index (p = 0.04), and smoothed pitch perturbation (p= 0.02). Among men, average fundamental frequency decreased from 141.93 Hz to 125.03 Hz; among women, this parameter decreased from 183.12 Hz to 164.22 Hz. Overall F0-tremor intensity index changed from 4.69% to 2.68%; amplitude tremor intensity index changed from 13.25% to 10.15%; jitter percent decreased from 5.00% to 3.81%; shimmer percent decreased from 14.18% to 11.85%; noise to harmonic ratio decreased from 0.50 to 0.36; and number of unvoiced segments decreased from 70.18 to 53.18. CONCLUSION: There were changes in the number of voice breaks, the main symptom of laryngeal adductor dystonia. Despite pre-vs. post-test decreases in various acoustic measurements, values remained above average.