Evoked responses originating from cochlea, brain stem, and cortex are clinically used for differential diagnosis of hearing losses. The diagnostic range and the reliability of the different ERA methods are discussed. In our clinic brain stem potentials recorded by a nonsurgical method have been used as a routine audiometric test in more than 900 cases. The procedure has proved to be easier than electrocochleography and gives nearly the same information about cochlear and middle ear function if there is no VIIIth nerve or lower brain stem damage. For topical diagnosis of the lower auditory pathway additional recording of ECoG is necessary. In the examination of a cortical deafness the recording of brain stem potentials yields the same result as the electrocochleography according to Aran (Fig. 2). In a case of an Apallic syndrome (Fig. 3) brain stem potentials are found only for high intensity clicks, and latencies are abnormally increased. The cochlear potentials simultaneously recorded from the promontory are quite normal. So damage of the brain stem is confirmed.