Brainstem auditory evoked response (BAER) testing is an electro-diagnostic test used to evaluate the hearing of dogs. It evaluates the components of the external ear canal, middle/inner ear cavities, cranial nerve and selected areas of the brainstem. It is a non-invasive procedure that takes 5 to 15 minutes to perform. In some circumstances, sedation is used. If the hearing threshold needs to be determined, more often in older patients, general anesthesia is recommended. From small subcutaneous electrodes and externally applied acoustic stimuli of different intensity, we record numerous waves, each of which represents composite neuronal activity.