The brain blood flow autoregulation (BFA) has been studied in normalcy and different variants of atherosclerosis in 97 subjects. Group 1 included 32 patients with obliterating atherosclerosis of the arteries of the low extremities with different stages of chronic artery insufficiency without hemodynamic lesions of brachiocephalic arteries; group 2 consisted of 30 patients wit different forms of chronic brain ischemia with hemodynamically significant unilateral atherosclerotic stenosis of the inner carotid artery (from 70 to 95%). The control group included 35 healthy volunteers aged 20-25 years. BFA parameters were assessed using the original technique worked out by the authors. In the normalcy, the BFA mechanism is able to maintain the constancy of perfusion pressure in the brain due to two major components. In the first stage, it is the aggravation of arterial blood inflow lasting for 1,5 min after the removal of pneumatic cuffs with the following surpassing increase of the venous blood outflow from the scull that decreases the tissue pressure. The most distinct BFA changes were seen in patients with hemodynamically significant stenosis of the inner carotid artery while patients with peripheral atherosclerosis had less marked BFA disturbances.