The aim of this study was to analyze cisplatin-induced ototoxicity in a recent study trial. Seventy-four patients who had received cisplatin for the treatment of osteosarcoma (median cumulative dose: 360 mg/m2) were investigated prospectively for ototoxicity in a multicenter trial. Hearing function was tested by audiometry. We evaluated the incidence and dependencies of hearing loss. After cessation of therapy, 51% of the patients showed a hearing loss of >20 dB in the frequency range of 4-8 kHz. Only in one patient a hearing loss was found at 2 kHz, and in none at 1 kHz. At a cumulative cisplatin dose of < or = 240 mg/m2, almost no ototoxicity was found. Incidence and magnitude of hearing loss increased significantly with a higher cumulative dose. Furthermore, hearing thresholds were significantly poorer in children <12 years. A further follow-up investigation showed only a marginal change in hearing function. We conclude that ototoxicity is moderate in our group of patients and probably irreversible.