The techniques of "evoked potentials" having produced an abundant and varied literature. In the light of personal experience with more than 4000 cases, the author gives pride of place to the field of neurologic pathology, in which evoked potentials can influence diagnosis, prognosis, therapy and physiopathologic interpretation. However, misunderstanding of the physical and physiologic parameters which may influence evoked potentials can discredit these techniques, which deserve more widespread use as an aid to diagnosis and not merely as an instrument of research.