We investigated the influence of cisplatin on spontaneous otoacoustic emissions (SOAEs) by measuring SOAEs, before and after cisplatin administration, in 18 ears of nine patients (one female and eight males) who had received chemotherapy with cisplatin for a brain tumor. No hearing loss was observed after cisplatin administration in eight ears. Before cisplatin administration SOAE was present in four out of these eight ears, and only mild frequency fluctuation was observed even after administration. In 10 ears, sensory neural hearing loss was observed after cisplatin administration. Before cisplatin administration SOAE was present in four out of these 10 ears, and SOAE decreased or disappeared in three ears after administration. In two ears, SOAE was not present before cisplatin administration, but newly appeared after administration. It was indicated that SOAE principally disappeared at the frequencies where the region of the outer hair cells responsible for the same frequencies was injured, but new SOAEs appeared at the frequencies where the region of the outer hair cells was not injured after cisplatin administration.