The side effects of the anti-cancer drug carboplatin on the cochlea in 65 patients with head and neck cancer were examined in the present study. A possible dependence of ototoxicity on the patient's age, the effect of pre-existing audiometric changes and the carboplatin dose were investigated. A therapy-induced sensory hearing loss was found in 32% of the patients. The average hearing loss was 15 dB and primarily involved the frequency ranges from 4 to 8 kHz. The degree of the hearing defects incurred was not influenced by the patient's age or pre-existing hearing defects but depended on the carboplatin dose used. The severity of carboplatin cochlear ototoxicity was moderate, so that no patient suffered a lack of hearing that was of social significance.