A pathological nystagmus, occurring during turning of the trunk in relation to the head, which is held stationary in space, clearly points towards a cervical origin of vestibular vertigo. Such a cervical nystagmus may have a vascular origin by the compression of the arteriae vertebrales, or a proprioreceptive origin via the upper neck joints, or it may possibly be due to functional disturbances of the upper cervical spine. The dynamic characteristics of the so-called cervico-ocular reflex can be examined only in patients with non-functioning labyrinths, since in a healthy person the reflex is so strongly suppressed that it cannot be analyzed any more. In five patients with isolated bilateral complete vestibular deficiencies, we found a strong cervico-ocular reflex. Detailed examinations showed that nystagmus occurred during turning of the body in relation to the head ("phasic neck reflex"). On the other hand, when remaining in the extreme positions, the proprioreceptive nystagmus does not persist. Contrary to this, a cervical nystagmus due to vascular causes shows a latency period after torsion of the neck and increases if the head remains in the extreme position. Before assuming a cervical origin of a vestibular vertigo, an examination for cervical nystagmus should be carried out. Such a cervical nystagmus is the only definite pointer towards a relation between an upper cervical spine syndrome and vertigo, which is sometimes assumed rather uncritically.