Adductor spastic dysphonia (SD) is a laryngeal dystonia characterized by a choked, constrained voice pattern with breaks in vocal flow. Treatment with a variety of therapies including speech and pharmacotherapy have minimal benefit; only one-third of patients undergoing recurrent laryngeal nerve section have benefitted at 3 years. We have used local injections of botulinum toxin (Botox) bilaterally into vocalis muscles in 42 patients with SD. Injections were through a teflon-coated hollow electromyography (EMG) recording needle. Unilateral small doses (2.5-3.75 U) were of no clinical benefit. Bilateral small doses resulted in sustained improvement lasting 84.4 +/- 9.3 days. The degree of improvement was 61.1 +/- 4.6%. Common side-effects included a brief period of breathy hypophonia (8.5 +/- 2.5 days) and a mild sensation of choking/aspiration of fluids (1.7 +/- 0.6 days); there were no serious adverse effects. Vocal cord paralysis was not necessary for benefit. Follow-up vocalis muscle EMGs revealed denervation. All patients responded to retreatment (longest follow-up 3.5 years). Patients with prior recurrent laryngeal nerve surgery and residual uncomplicated dysphonia had similar results. Our results indicate that local injection of low-dose Botox is the treatment of choice for SD.