Objective: Increased vertebral artery vascular resistance is proposed to affect neural activity in centers of the brain stem implicated in autonomic control and may lead to arterial hypertension (1, 2). Atheroma of the vertebral rather than of the internal carotid artery is associated with hypertension (2). We hypothesized that i) age-related reductions in flow would be greater in the vertebral artery than in the internal carotid artery, ii) orthostatic stress reduces internal carotid but not vertebral artery flow, and iii) CBF is related to maximal oxygen uptake (VO2max) as an indication for effect of aerobic fitness on “brain health”.Methods: The study included young (n = 22; 24 ± 1 yrs.; MAP 78 ± 2 mmHg (mean ± SE)) and elderly men (n = 16; 70 ± 1 yrs.; MAP 94 ± 4 mmHg) and measurements were conducted during supine and semi-seated rest and during submaximal exercise. MAP, heart rate and cardiac output were determined non-invasively by pulse-contour analysis (Modelflow). Near-infrared spectroscopy was used to determine frontal lobe oxygenation (ScO2) and middle cerebral artery mean flow velocity (MCA Vmean) was evaluated by transcranial Doppler sonography. Bilateral internal carotid and vertebral artery blood flow was determined by duplex ultrasound. Analysis of variables was by two-way ANOVA with the main factors age (young vs. elderly), intervention (supine and semi-seated rest, 15 W exercise, and peak workload) and their interaction. Differences between the two age groups were evaluated by a two-tailed t-test. Linear regression evaluated an association between CBF and VO2max.Results: During supine rest ScO2 (77 ± 2% vs. 68 ± 1%; P = 0.0002), MCA Vmean (60 ± 3 vs. 48 ± 3 cm/s; P = 0.0047), bilateral internal carotid (680 ± 26 vs. 607 ± 26 ml/min; P = 0.0593; 11 ± 6%) and vertebral artery flow (219 ± 11 vs. 136 ± 17 ml/min; P < 0.0001; 38 ± 9%), and thus CBF (900 ± 31 vs. 734 ± 37 ml/min­; P = 0.0019) were lower in the elderly. CBF was associated with estimated VO2max in the elderly (P = 0.0406). In a semi-seated position internal carotid (-9 ± 2%; P < 0.0001) but not vertebral artery flow decreased.Conclusion: CBF is better preserved in aerobically conditioned elderly individuals supporting importance of exercise for “brain health”, while the age-related decrease in CBF affects vertebral more than internal carotid artery flow which may have implications for blood pressure regulation. Preserved vertebral artery flow during orthostatic stress suggests an importance for cardiovascular control.