Botulinum A toxin for the treatment of adult-onset spasmodic torticollis. Thirty-five patients with adult-onset idiopathic torticollis were treated by local injections of botulinum A toxin into dystonic cervical muscles. Substantial improvement with respect to reduction and elimination of pain was found in 81 percent, improvement in posture deformity and involuntary spasms in 70 percent, increased range of motion of the neck in 78 percent, reduction in visible sternocleidomastoid hypertrophy in 86 percent, and improvement in tremor in 65 percent. The syndrome was divided into four subtypes based on pattern of dystonic muscle groups involved in the dystonia, head and shoulder posture, and sternocleidomastoid muscle hypertrophy. Injection strategy based on this subdivision is described. 