In a prospective study, we have examined the efficacy of intracutaneous injections of botulinum toxin in Frey's syndrome. In a controlled study, the long term results after surgical treatment for parotid tumors were investigated in 98 consecutive patients. Patients, who reacted positive by Minor's iodine-starch test, and who had subjective complaints too, were offered treatment. A total of four patients entered the study. The affected area was visualised by Minor's iodine-starch test. The coloured areas were injected with botulinum toxin (Botox) 2.5 U/0.1 ml. We injected 0.5 U/cm2. The distance between each injections points was 1 cm. All patients became free of symptoms. The injections were given with little discomfort to the patients and no side effects. At the control one year after the injections three patients had minor recurrent complaints, which were treated successfully by reinjections. Botulinum toxin injections are thus safe and effective in the treatment of FS.