In 1978, Kemp originally recorded stimulated otoacoustic emission in the external auditory canal using miniature microphone set. Now, otoacoustic emission is under practicing as one of routine audiologic procedures. It is possible to perform screening acoustic cochleography in about few minutes. The technique is also useful for characterizing mechanical status of a cochlea, which needs long term monitoring and is promising as a fast, objective and noninvasive audiologic procedure. However, accurate interpretation of the emission response must be based on the basic properties of the emission according to age groups. In this study, the properties of emissions were investigated in 60 ears from 30 adults with normal middle and inner ear function between 20 and 30 years of age. The results were as follows ; 1) Click evoked-toacoustic emission (CEOE) could be recorded in all adult normal ears. 2) The averge stimulus threshold of echo response in normal ears was 65.9 dB peak SPL. 3) The amplitude of CEOE response was correlated with the click stimulus level in non-linear pattern. 4) The CEOE in normal ear shows a broad band spectrum in spectral analysis with three or more multiple narrow band peaks. 5) The peaks of CEOE in spectral analysis were clusted between 1 and 2 kHz in spectral analysis.