The head of guinea pig was irradiated with 60Coγ-ray and a single dose of irradiation was 90 Gy and 70 Gy in two groups, respectively.Two h after irradiation, the threshold shifts were 12.5 dB and 9 dB, and the auditory cortical evoked response (ACER) maximum post-irradiation amplitude exceeded the maximum prc-irradiation value by 20% and 37%.Six h later, the threshold shift increased to 37 dB and the maximum amplitude decreased to the level of pre-irradiation in the 70 Gy group.Right auditory bulla area wa...