PURPOSE: Several therapeutic approaches have been introduced and tried to treat Frey syndrome following parotidectomy. However they were not proved as an effective treatment. A new therapeutic modality using botulinum toxin injections was presented previously by several study groups. But, the duration of the demonstrated positive effect was essentially unknown so far. The purpose of this clinical investigation is to demonstrate the effectiveness of Botulinum toxin type A(BTXA) in patients with Frey syndrome. METHODS: For this study, 12 patients were treated, They were assessed with the Minor's iodine-starch test and interviewed before and after treatment. Botulinum toxin is injected with 1.0cm2 apart into the skin where symptoms of Frey's syndrome has manifestated. The patients were classified according to the concentration of botulinum toxin and dosage of botulinum toxin. RESULTS: The outcome measures were the time of reappearance of gustatory sweating(subjective study), and the results of an Minor's iodine-starch test(objective study) of 3 weeks, 3 months, 6 months, 9 months, 12 months after treatment. This treatment was effective in all groups of patients. The concentrations and the amount of dosages did not affect the treatment. But high concentration produced faster effectiveness in subjective. CONCLUSION: Botulinum toxin type A(BTXA) for Frey syndrome is easy, convenient and effective withouts severe complication. And the patients has no difficulty and limitation in their life.