Permanent or transient reduction of the blood flow to the brain is often responsible for dizziness and occasionally sensorineural hearing loss. So far the diagnosis of this condition has been made by angiography, either carotid or vertebral arteriography, but there is a justified reluctance of subjecting unselected patients to this invasive procedure. It is the purpose of this paper to present a new approach to the diagnosis of cerebral vascular insufficiency based on a three-step protocol. The two initial steps are formed by noninvasive techniques and may be used for the selection of those cases requiring additional diagnostic procedures. 1) Cerebral hemodynamic evaluation provides a physiologic assessment of the direct carotid and indirect carotid and vertebral blood flow. It includes ocular plethysmography and ophthalmodynamometry obtained with the patient supine and erect, without and during carotid compression. 2) Computerized tomography allows an evaluation of the brain substance and of the changes produced by vascular insufficiency such as brain atrophy, infarcts and encephalomalacia. A new form of radiographic assessment based on a dynamic evaluation of regional blood flow will be introduced in this paper. 3) Carotid and vertebral arteriograms are performed only on those cases demonstrating a significant cerebral vascular insufficiency by the previous tests and in cases where corrective surgery is contemplated.