The method of electroencephalography was used for examining 86 patients with clinical signs of vertebrobasilar blood supply disorders and bulbopontine localization of ischemic phenomena. Light to moderate diffuse alterations were found which manifested themselves, on the one hand, in a reduction in tension with a tendency toward desynchronization of the alpha rhythm and, on the other, in interspersed theta waves, sometimes with temporal localization. The determination of the location of the vascular process depends upon both the clinical syndrome and the performance of function tests during the electroencephalographic examination. The disproportion between the excellent organization of the bioelectrical activity and the severe clinical picture is sufficient reason to consider vascular damages to the pontobulbar portion of the brain stem.