This term is used for describing disturbances of blood flow in the vertebral and basilar arteries due to atherosclerotic lesions causing stenosis or occlusion of these arteries. Clinical patterns of the resulting disturbances include transient symptoms, mainly vertigo, and stabilized syndromes with evidence of brain damage in this blood supply area. The purpose of the study was assessment of the blood flow in this vascular bed by means of dynamic computerized tomography (DCT) in relation to clinical signs, and a comparison of the results with those of similar DCT examinations in cases of circulatory disturbances in the carotid arteries. The study was carried out on 40 patients (20 with stabilized syndromes, 10 with transient disturbances and 10 with ischaemic episodes in the carotid artery supply. DCT abnormalities were found in 90% of patients with stabilized syndromes and in 40% of those with transient ischaemia. DCT may be an auxiliary diagnostic methods and may confirm the presence of vertebrobasilar circulatory failure. Normal result is not ruling out presence of changes in this arterial system.