In our research, using two electrophysiological methods (registration of auditory brainstem response, distortion product otoacoustic emission) we were estimating auditory function of immature rabbits in response of introduction of therapeutic doses of vancomycin (15 mg/kg daily, 7 days). Damaging action was reflected in a functional condition of peripheral department of the acoustic analyzer. According to the brainstem auditory evoked potentials it expressed in elevation of thresholds of the first peak of ABR and shortening of peripheral time of carrying out. According to distortion product otoacoustic emission — a decreased amplitude caused the acoustic answer to frequency of 4 kHz and change of speed of maturing of functioning of outer hair cells on frequencies of 2, 4, 6 kHz.