A prospective controlled clinical study was carried out at the Department of Ophthalmology and ENT, Inönü University Medical Faculty, Turgut Ozal Medical Center, Research Hospital, to evaluate the audio-vestibular involvement in patients with Behçet's syndrome compared with controls. Twenty-five consecutive patients with Behçet's syndrome (mean age +/- SD, 34.96 +/- 8.50) and 20 age- and sex-matched healthy volunteers (hospital staff) as control subjects (mean age +/- SD, 34.45 +/- 9.16) were included in this study. Behçet's patients were divided into two groups according to the number of criteria, complete (all four major criteria) and incomplete (three major criteria without ocular involvement). The groups were compared with each other or controls regarding inner ear involvement. Audiometric pure-tone thresholds at 125 to 8000 Hz were obtained in all subjects in both groups, and pure tone average (PTA) hearing thresholds were calculated for the middle, high and low frequencies. In addition, short increment sensitivity index (SISI), tone decay and BERA examinations were performed in all Behçet's patients. Sensorineural hearing loss (SNHL) was present in six of 25 patients with Behçet's syndrome. Two Behçet's patients had unilateral total SNHL, two had bilateral moderate level SNHL, one had bilateral low-frequency SNHL and one bilateral high frequency SNHL. In two, BERA, and in five SISI, examination disclosed inner ear involvement. In control subjects, the past medical history was normal and there was no consistent audio-vestibular complaint. Their PTA thresholds were all in the normal range. Otoscopic examination findings were normal, with intact, mobile tympanic membranes in both groups. The present study showed that audio-vestibular involvement is not infrequent in Behçet's syndrome compared with age- and sex-matched healthy controls, and it is under-estimated. All Behçet's patients should regularly be followed by an otolaryngologists and be given information about the possibility of inner ear involvement. According to our results, hearing loss occurs more often in older patients and also in the complete form of Behçet's syndrome.