Function of the nonspecific brain structures (NBS) was examined in 49 patients distributed into two groups: with initial manifestations of brain blood supply insufficiency (IMBBSI) (n = 28) and atherosclerotic encephalopathy (n = 21). Use was made of an approach with the use of autonomic and psychological techniques as well as of a polygraphic recording of the electrophysiological parameters of nocturnal sleep. It has been established that both groups patients manifest NBS dysfunction. However, its qualitative characteristics were found to differ noticeably in IMBBSI and AE. The patients with DE demonstrate more remarkable inhibition of the synchronous mechanisms that regulate both phases of nocturnal sleep and reciprocal enhancement of the activity of the systems of the ascending nonspecific brain activation. The autonomic and psychological data agree with the electrophysiological data obtained. The conclusion is drawn that in patients with cerebrovascular insufficiency, the NBS systems are first of all involved in the pathological process. This is of importance for both the diagnosis and further studies into the pathogenesis of different forms of cerebrovascular insufficiency.