Objective To analyze the characteristic and the clinical application of high -frequency stimulation ABR for the patients with unilateral sudden deafness .Methods 40 patients aged 17~45 with unilateral sudden deaf-ness(40 health ears ,subject group)and 20 normal volunteers (40 ears ,control group)were selected to receive high and low frequency stimulation ABRs and pure tone audiometry .Results There were no statistical differences be-tween subject group and control group in pure tone audiometry .The wave Ⅰlatency of high -frequency ABR was longer in the subject group than that in the control group(P<0 .001) .The abnormal rate of Ⅰ - Ⅴ interval between high and low frequency stimulation ABRs was 62 .5% (25/40) in the subject group ,and 5% (2/40) in the control group .There were statistical differences between the two groups (χ2 =29 .574 ,P<0 .001) .Conclusion The waveⅠlatency of high-frequency ABR was longer and the abnormal rate of Ⅰ - Ⅴ interval markedly increased in the health ear of patients with unilateral sudden deafness .This may suggest that the contralateral ear may have an ab-normal blood supply of the inner ear when single side sudden deafness happened .High frequency stimulation ABR can be used to detect the potential changes of contralateral ear before the hearing loss occurred .