The symptom of sudden tilting of the visual surroundings is described in detail based on experience with five patients. Patients perceive the visual fields as suddenly turning through a variable arc, most frequently 90-180 degrees, usually associated with dizziness. In three patients with vertebral-basilar artery disease, visual tilting was more closely related to local pontomedullary ischemia than to posterior cortical ischemia. It is suggested that most instances of this illusion are due to disorders of the vestibular-otolithic apparatus or its central connections, most frequently from vertebral-basilar ischemia.