Stuttering is a movement disorder of speech-motor control characterized by inappropriate timing of lingual, labial, laryngeal, and respiratory muscles. Treatment for adult stutterers have included traditional and non-traditional behavioral and psychiatric modalities, many with good initial success but all with limited long-term benefit. Recent trials of botulinum toxin injection was somewhat favorable. In this study, the authors injected 5-8 U of botulinum toxin into the thyroarytenoid muscle bilaterally in cases of disabling stutterers. Evaluation after 4 weeks of injection, 80% of the patients was improved more than one positive scale. However, no one was improved to almostly normal range.