BACKGROUND AND OBJECTIVES: The mechanism of the noise damage to the cochlea is not fully understood in spite of many studies. The morphological changes in a noise stimulated model show various features relating to the duration of the exposure and sound intensity. Until now there had been a lot of the morphological studies on noise induced hearing loss models, but only a few reports of single blast injury of more than 150 dB. MATERIALS AND METHOD: We observed with a transmission electron microscope by using the microslicing technique for minimizing the tissue injury and successful hair cell counting in resin embedded cochlea of the guinea pig, stimulated by a 178 dB single blast wave. RESULTS: The area of hair cell damage in L.M. showed stereocilia bending at 24 hours, proliferation of Hensen's body, subsurface cistern in outer hair cell and mitochondria proliferation in inner hair cell within 2wks. The area of no hair cell damage in L.M. showed minimal changes in E.M., as well. CONCLUSION: These results suggest that the 178 dB single blast wave injury may not cause severe distortion of the organ of Corti in the guinea pig and thus the compensation process can be advanced gradually.