We evaluated the effects of olmesartan, an angiotensin II receptor blocker (ARB), on cerebral blood flow (CBF) in elderly and hypertensive subjects. Ten subjects with first- or second-degree essential hypertension (mean age, 70.5 years) underwent brain single-photon emission tomography (SPECT) scanning with Tc-99m-ethyl cysteinate dimer before and after a 24-week course of olmesartan. Mean systolic blood pressure (SBP) was 156.2 +/- 9.9 mm Hg, and mean diastolic blood pressure (DBP) was 89.1 +/- 5.5 mm Hg. No subject had any abnormalities on neurologic examination or previous history of stroke or cardiovascular disease. Before olmesartan administration, the hypertensive subjects had approximately 15% less whole brain CBF compared with age-matched normotensive controls. Regional CBF was decreased by 11%-20% in the frontal, parietal, temporal, and posterior lobes. Olmesartan treatment significantly decreased SBP to 130.4 +/- 4.2 mm Hg (P < .001) and DBP to 78.2 +/- 7.0 mm Hg (P < .001). After 24 weeks of olmesartan treatment, CBF of whole brain and regional CBF of the frontal, parietal, and temporal lobe were similar to those of control subjects. Our brain SPECT data indicate that olmesartan restores brain hypoperfusion in elderly and hypertensive patients without organic damage. This ARB may have a favorable potential for cerebrovascular circulation, in addition to a blood-pressure lowering effect.