The authors did a study to clarify the ototoxic effect of Cis-platinum by comparing the hearing level after infusion of Cis-platinum by Hong's (1979) method with the hearing level before infusion of Cis-platinum and admitted to the Dept. of Otolaryngology of Yonsei University Hospital during 2 years and a half from July. 1979 to March. 1982 and the following results were obtained. 1) The results of auditory evaluation, using the pure tone average, hearing loss of 4 kHz and 8 kHz, Speech Reception Threshold, PB sore, SISI showed that the difference of dosage does not change the hearing level after infusion of Cis-platinum and before infusion of Cis-platinum. 2) Cis-platinum had no effect on the hearing level of patients with conductive hearing loss, or with sensorineural hearing loss, as well as with normal hearing level. 3) The infusion of Cis-platinum did not cause any change in creatinine clearance, creatinine, uric acid, but only one case showed that Cis-platinum caused severe nephrotoxicity. 4) The infusion of Cis-platinum did not cause any change in hemoglobin, leukocyte count, platelet count and there was no correlation with the amount of infusion. 5) To see the side effect of hydration practiced with the infusion of Cis-platinum, the electrolytes, particularly the K level in the serum was measured. But the results did not show any change. 6) Judging from the results of this study mentioned above, ototoxicity caused by infusion of Cis-platinum can be prevented by sufficient hydration. Also the results might say that the appropriate method of infusion of Cis-platinum might be effective in the patients with head and neck cancer who had sensorineural hearing loss for whom the infusion of Cis-platinum has been absolutely contraindicated.