The amplitude of the slow component is one of the important parameters of vestibular nystagmus. In the present paper an attempt is made to examine the diagnostic significance of this parameter with respect to spontaneous, provoked and experimentally induced nystagmus. Particular interest is taken in the influence of unspecific and specific factors upon nystagmus amplitude such as optic fixation, alertness, habituation, compensation phenomena, peripheral and central vestibular lesions. Based upon statistical evaluation of the results of nystagmographic investigations, carried out in normal individuals as well as in patients suffering from a vestibular disorder, a further attempt is made to establish more reliable facts indicating the presence of a pathologic modification of nystagmus amplitude.