The systematic use of reconstruction of cochlea combined with physiologic analysis of hearing have made it possible to correlate acoustic trauma and inner ear damage. The objective of this study was to determine hearing levels and morphologic change of the inner ear before and after acoustic exposure. Morphological analysis of cochlear hair cell was performed using scanning electron microscopy while the auditory function was measured with the auditory brainstem response(ABR). Ten guinea pigs were used for this study, five for control group and five for experimental group. Acoustic trauma was applied to the experimental group with 1KHz pure tone, at 125dB for 90 minutes. ABR was determined before and after the acoustic exposure. All guinea pigs were sacrificed four weeks after the acoustic exposure. The results were as follows : 1) Temporary threshold shift showed no remarkable difference in each frequency, however, the extents of hearing recovery were different in each frequency. 2) The most severely damaged portion of outer hair cells was from 12.0mm to 12.9mm, which was corresponding to 1.0-1.5KHz in cochleogram. 3) Same portions were damaged in both outer hair cells and inner hair cells, however, inner hair cells have sustained less damage than outer hair cells. 4) The most severely damaged row of outer hair cells was third row. 5) As one approached to the center of damaged portion, more severe destruction of hair cells could be observed. However, the inner hair cells have sustained less severe destruction than outer hair cells. 6) Hair cell destruction was not uniformly observed in areas representing the frequency of hearing loss.