We reviewed 36 patients with gentamicin vestibulotoxicity to determine its relationship to gentamicin dosage, serum gentamicin levels, and the development of gentamicin nephrotoxicity. Thirty of the patients had received intravenous or intramuscular gentamicin; six had received intraperitoneal gentamicin. Sixteen of the 30 patients treated with intramuscular or intravenous gentamicin had received less than the recommended maximum dose of 5 mg/kg/day for less than the recommended maximum period of 10 days. Nephrotoxicity as well as vestibulotoxicity developed in 16 of these 30 patients. Gentamicin vestibulotoxicity was not recognized before discharge from hospital in 32 of the 36 patients. We conclude that as far as the vestibular system is concerned there is no safe gentamicin dose and no safe serum gentamicin level, and there is an increased risk of vestibulotoxicity in patients in whom nephrotoxicity develops. Physicians who use gentamicin should become more aware of the clinical features of vestibulotoxicity because stopping gentamicin as soon as symptoms of vestibulotoxicity appear could prevent permanent impairment of vestibular function.