From March 1984 through March 1989 we performed 235 audiometric tests on 39 children with malignant brain tumors who were treated with cisplatin 100 mg/m2 every 3 weeks for three courses and vincristine weekly for 9 weeks followed by cranial irradiation. Twenty-eight of the 39 children had sufficient serial testing for evaluation of ototoxicity secondary to cisplatin. Following the third cisplatin treatment (300 mg/m2 cumulative dose), 20% of the assessable children had hearing loss limited to the high frequencies of 6,000 to 8,000 Hz, 16% had hearing loss beginning at 3,000 to 4,000 Hz, and three children (11%) had loss within the speech frequencies beginning at 1,000 to 2,000 Hz. Eighteen of 19 children (95%) who were evaluated comparatively at a median of 15 months following radiation showed no significant change from preradiation testing. There was no correlation between hearing loss and patient age. We conclude that cisplatin ototoxicity was acceptable and that radiation therapy does not increase the ototoxicity of cisplatin when the drug is given before, instead of following, cranial irradiation.