Effect of White Noise on Cochlear Microphonics (CM) was studied in 10 guinea pigs. Each guinea pig was exposed to 100 dB SPL White Noise for 30 minutes. And then, CM response was measured on Round window membrane using extracochlear single electrode method at every 15 minutes interval until 90 minutes after noise exposure. The results are as follows ; 1) Before Noise exposure, CM potential stimulated by 100 dB pure tone was 60.76±13.6 μV at 500 Hz, 52.08±9.9 μV at 1,000 Hz and 16.12±2.5 μV at 2,000 Hz. 2) CM potential was gradually decreased until 30 minutes after white noise exposure. After then, partially recovered to near 90% level of control at 90 minutes after exposure. 3) There was no significant statistical difference in CM loss and Recovery among 3 frequencies : 500, 1,000 and 2,000 Hz(p<0.05). 4) Some individual variation of CM response was identified in several guinea pigs.