Recently, Cochlear Hydrops Analysis Masking Procedure (CHAMP), simply analyzing technique from the stacked auditory brainstem response (ABR), proved to be able to separate normal control from definite Ménière’s disease groups. CHAMP test is based on the hypothesis that the cochlear hydrops alter the mechanical properties of the basilar membrane. Cochlear hydrops or endolymphatic hydrops results in increased traveling wave velocity and a basalward shift in the peak of the traveling wave in cochleas with presumed normal basilar membrane elasticity. This alteration of the properties can be found in patients diagnosed with Ménière’s disease because the underlying pathophysiologic state in Ménière’s disease is endolymphatic hydrops and causes impaired high-pass noise (HPN) masking of auditory brainstem responses to clicks. When the ABR response were obtained from the click alone and click with 8, 4, 2, 1, 0.5 kHz HPN masking conditions, the cochlea is successively masked from 8 kHz and higher and down to 0.5 kHz higher, the peak latency of wave V usually increases with restricted response region. However, in Ménière’s disease patients, the masking noise does reduce the amount of neural activity, the noise does not mask sufficiently the high frequency regions of the cochlea that dominate the latency measure. This response pattern where the latency of wave V changes little as the cochlea is progressively masked from 8 to 0.5 kHz is referred to the undermasked pattern. The undermasked component in the response to clicks with 0.5 kHz HPN masking and wave V in the response to clicks presented alone clearly distinguished between normal and Ménière’s disease groups with less than 0.3 ms ‘wave V latency delay’ in the latter group. Considering the difficulty of determining the undermasked component, ‘complex amplitude ratio’, the ratio of the amplitude of wave V in the subtracted waveform (click alone-0.5 kHz HPN) to the amplitude of wave V in the response to clicks alone was also developed. Although more investigations are needed for utilizing clinically CHAMP seems to be valuable tool for discriminating active Ménière’s disease in individuals objectively with high sensitivity and specificity. KEY WORDS：Endolymphatic hydrops·Me´nie`re’s disease·High pass noise (HPN)·The undermasked pattern·Cochlear Hydrops Analysis Masking Procedure (CHAMP).