Cochlear activity was evaluated by means of otoacoustic emission in patients with normal hearing and insulin-dependent diabetes mellitus. Twenty diabetic subjects were studied by recording click evoked otoacoustic emissions (TEOAE) and distortion products otoacoustic emissions (DPOAE) 2fl-f2 and comparing the results with those obtained in a control group of non-diabetic with normal hearing. The results obtained in the diabetic group showed a statistically significant decrease in mean amplitude, in the amplitude of every click evoked otoacoustic emissions and in the mean amplitudes of various distortion products compared with the control group. These findings suggest the presence of cochlear disorders in diabetic patients, probably produced by impaired functional properties of the outer hair cells.