A study of the functional state of cerebral hemodynamics (blood flow velocity and hemodynamic reserve in the basilar artery) using transcranial Doppler with nitroglycerine test has been carried out in 18 patients with ischemic stroke in vertebrobasilar circulation and 20 patients with and/or symptoms suggestive of posterior circulation disease. Significant decrease of the parameters of cerebral hemodynamic reserve was shown in patients with a history of ischemic stroke and also in patients with atherosclerotic obstructive lesions of the vertebral arteries. On the other hand in patients with the anomalies of the vertebral arteries (kinking, hypoplasia) blood flow in vertebrobasilar circulation was normal. Therefore these patients need not of the surgical preventive treatment