A review of the literature shows the extreme frequency of nystagmus and changes in vestibular reflexes in disseminated sclerosis. During the course of this disease, it is possible to detect nystagmus in at least two-thirds of cases and in a similar proportion there are changes in vestibular reflexes, usually a hyperreflexia, especially in the early phases of disseminated sclerosis. Subjectively the patients rarely complain of vertigo and such symptoms are in any case part of the early form of the disease. On the other hand, disorders of balance are much more frequent but the factors involved are numerous, and the role of the vestibular system is often debatable. Electronystagmography and oculography demonstrate the extreme frequency of spontaneous or fixed gaze nystagmus in this disease, as well as the extreme frequency of changes in conjugated eye movements; changes in reflex, voluntary and automatic conjugated eye movements. As a matter of fact, there are many kinds of nystagmus which are not related to any changes in the vestibular system, but which are rather more part of the overal changes of conjugated eye movements. Seen in this light, electronystagmography and oculography, by exploring the different kinds of conjugated eye movement, can help decisively in the diagnosis of disseminated sclerosis by revealing changes which reflect damage to the brain stem, lesions which are clinically very often silent. In this way the diagnosis of disseminated sclerosis may be confirmed. Furthermore, electronystagmography can easily suggest another diagnosis, other than the early form of disseminated sclerosis of the vestibular type.