A developing method for testing auditory function and detecting neurological disorders is the brain stem auditory evoked response (BAER) to sound stimuli. Elicitation of the BAER is noninvasive and produces an objective measurement of a subject's auditory function. Basic principles of this technique and normative data are presented in this paper. It was found that the BAER can detect asymptomatic high-frequency hearing losses. The sensitivity of this technique makes it an ideal method for evaluating functional hearing losses. Two illustrations of functional hearing losses are presented. Wave V's threshold, latency and amplitude, along with comparisons between the auditory (subjective) and BAER threshold, are useful parameters when testing for nonorganic hearing disorders. However, this sensitivity to minor hearing losses makes it imperative that all control subjects be established as normal by an audiogram. A mere negative history for hearing disorders is felt by the authors to be an inadequate screening of control subjects.