Ageing reduces cerebral blood flow (CBF), while mean arterial pressure (MAP) becomes elevated. According to 'the selfish brain' hypothesis of hypertension, a reduction in vertebral artery blood flow (VA) leads to increased sympathetic activity and thus increases MAP. In twenty-two young (24 +/- 3 years; mean +/- SD) and eleven elderly (70 +/- 5 years) normotensive men, duplex ultrasound evaluated whether the age-related reduction in CBF affects VA more than internal carotid artery (ICA) blood flow. Pulse-contour analysis evaluated MAP while near-infrared spectroscopy determined frontal lobe oxygenation and transcranial Doppler middle cerebral artery mean blood velocity (MCA V-mean). During supine rest, MAP (90 +/- 13 versus 78 +/- 9 mmHg; P<0 center dot 001) was elevated in the older subjects while their frontal lobe oxygenation (68 +/- 7% versus 77 +/- 7%; P<0 center dot 001), MCA V-mean (49 +/- 9 versus 60 +/- 12 cm s(-1); P = 0 center dot 016) and CBF (754 +/- 112 versus 900 +/- 144 ml min(-1); P = 0 center dot 004) were low reflected in VA (138 +/- 48 versus 219 +/- 50 ml min(-1); P<0 center dot 001) rather than in ICA flow (616 +/- 96 versus 680 +/- 120 ml min(-1); P = 0 center dot 099). In conclusion, blood supply to the brain and its oxygenation are affected by ageing and the age-related decline in VA flow appears to be four times as large as that in ICA and could be important for the age-related increase in MAP.