Abstract: In order to accurately evaluate the quality and quantity of hearing loss in diabetics and to identify the site of the lesion of hearing impairment, Bekesy audiometry, impedance audiometry with stapedius reflex test, speech discrimination and recording of electrocochleography （ECochG） and brainstem auditory evoked potentials （BAEP） were performed in 43 patients with diabetes mellitus. The results were compared with those of 43 sex-and age-matched non-diadetic subjects. The results showed that the average acoustic thresholds and AP reactive thresholds were significantly elevated in the diabetic subjects as compared with those in the controls. There was a signicant decrease in mean PBMAX% in the diabetic group. The incidence （48%） of hearing impairment in diabetics is higher than that （10%） in controls. The diabetic hearing impairment is characterized by bilaterally symmetrical high tone sensorineural deafness. The site of the lesion of the diabetic heaeing impairment is chiefly in cochlea, and less frequently in the acoustic nerve and brainstem auditory pathway.