Seventy five patients with lacunar infarcts (LI) in the presence of arterial hypertension (AH), 40 patients with AH without signs of lacunar syndromes, and 25 apparently healthy individuals were examined to study the functional status of cerebral circulation in LI and AH. The site and sixes of ischemic foci were specified by the results of brain computed tomography. The functional status of cerebral circulation was evaluated by Doppler transcranial evidence, by using the compression test. There was a reduction in the linear blood flow velocity (LBFV) in the middle cerebral arteries (MCA) and an increase in the pulsation index in the group of patients with LI as compared with the controls. The autoregulation reserve estimated by the overshoot coefficient was preserved in all the examinees. The greatest differences between groups were found in estimating the reserves of col lateral circulation (CC). The signs of decompensated CC were considered to be a less than 23,4 cm/sec decrease in LBFV in the MCA during compression of the common carotid artery (V 2 ). a greater than 10,8 sec increase in the recovery time of the baseline LBFV after compression (T), discriminant equation values more than 0,728 at D = 0.186 x T — 0,102 x V 2 + 1,116. The decompensated type of CC was revealed in 67.556 of the patients with LI versus 17,5 % of those with AH and 8 % in the control group. It is suggested that decompensated CC detected by the compression serves as a marker of the parallel development of angiopathy of connective and perforating arteries and as the background for LI development.