The role of botulinum toxin as a therapeutic agent is expanding rapidly in otolaryngology. Botulinum toxin is a protease that blocks the release of acetylcholine from nerve terminals. Its effects are transient and nondestructive, and largely limited to the area in which it is administered These effects are also graded according to the dose, allowing for individualized treatment of patients and disorders. Botulinum toxin has been used primarily to treat disorders of excessive or inappropriate muscle contraction. In the field of otolaryngology, these include spasmodic dysphonia, oromandibular dystonia, and blepharospasm, vocal tics and stuttering, cricopharyngeal achalasia, various tremors and tics, hemifacial spasm, temporomandibular joint disorders and a number of cosmetic applications. Botulinum toxin treatment has recently begun to show some benefit in the control of pain from migraine and tension headache. It may also prove useful in the control of autonomic dysfunction, as in Frey syndrome, sialorrhea, and rhinorrhea. In over 20 yews of use in humans, botulinum toxin has accumulated a considerable safety record, and in many cases represents relief for thousands of patients unaided by other therapy.