The aim of a documentation in electronystagmography, that is to record as complete and definite as possible the information of a nystagmus relative to all its distinctive marks, hitherto has been reached just as little as the attempt, to develop a fine-quantitative investigatory method suitable for standardization for medical practice. The sources of error caused by the equipment and of physiological nature within a recorded nystagmus trace are exposed and illustrated by respective examples. Outgoing from the theory of the rotatory nystagmus based on the rotation test of the human vestibular system the fundamentels are developed for a complete evaluation method of an electronystagmogram including the elimination of artefacts by the authors' own research work in this field. However the pointed out problems of the electronystagmography are not yet answered in the clinical diagnostic of vestibular diseases, the systematic examination of spontaneous nystagmus and provoked nystagmus still represents the most important, most profitable and well-grounded part of the vestibular investigation in the medical practice.