Several therapeutic approaches exist to treat gustatory sweating (Frey's syndrome) following parotidectomy. Because of the lack of effective treatment, a new therapeutic modality using botulinum toxin injections was presented previously by our group. The duration of the demonstrated positive effect was essentially unknown so far. Based on our experiences using this technique since December 1993, the purpose of this clinical investigation was to make an up-to-date report and demonstrate the duration of effect of BOTOX injections in patients with severe gustatory sweating. Nineteen patients with severe gustatory sweating have been treated with BOTOX by intracutaneous injections into the affected skin areas. The maximal follow-up time was 33 months. The results were obtained by interviews and controls using Minor's starch iodine test. In all treated cases (n = 19 patients, 22 treated sides) gustatory sweating ceased completely within 2 days. Side effects were absent. In 12 patients gustatory sweating reappeared. The mean duration of effect was 17.3 months (subjective personal communication of 18 patients). Findings show that intracutaneous injection of BOTOX is a highly effective, safe, and minimally invasive treatment of Frey's syndrome with long-lasting therapeutic effect.