Fifty-four patients with metastatic cancer were followed audiometrically during high-dose (100-120 mg/m2) cisplatin chemotherapy. Eighty-one percent of the patients showed significant changes in air-conduction hearing thresholds after completion of therapy. Thirteen percent sustained a significant hearing handicap. An interindividual variation was found, ranging from severe hearing loss after the first course to unaffected hearing after three courses. The ototoxic effect was not increased by pre-existing hearing loss, but was slightly increased by age. The risk was determined more by the amount of the single dose than by the cumulative dose. The further ototoxic effect could not be predicted on the basis of the audiogram after the first course. Peak plasma concentration of platinum was measured in eight patients, and no ototoxic changes were noted below a concentration of 1 microgram/L.