The accuracy of the brainstem evoked response audiometry(BERA) for the otoneurological differential diagnosis is above 90% in patients whose hearing loss are 80dB HL or less. But in patients whose hearing impairment are 80dB HL or more, BERA cannot be used in determining of the exact site of the lesion because the interpeak latencies cannot be obtained. Electrocochleography(ECochG), especially cochlear microphonics(CM) can provide information which can assist in such occasions. In order to use CM for this purpose, the authors studied characteristics, thresholds, amplitudes and latencies of CM for the 4KHz clicks and tone pips of 1KHz through 4KHz at various intensities and with different polarities. The results are follows : 1) The waveforms of CM were similar to those of the stimuli. When the polarities of the stimuli were reversed, the polarities of CM werer also reversed. 2) The mean thresholds of CM ranged from about 54.5 to 57.0dB HL to the tone pips and significant differences were not observed for the different frequencies and polarities. Thresholds for the 4KHz clicks were lower than those for 4KHz tone pips. 3) The latencies of CM were neither affected by the stimulus intensity nor by polarity. However, the latencies were increased as the stimuli frequencies decreased. 4) The amplitudes of CM were increased as the stimulus intensities increased, and decreased as the stimulus frequency increased. Significant differences were not observed in amplitudes when the signal polarities were reversed.