In an attempt to elucidate the mechanism by which hypertension acts as a risk factor for major non-haemorrhagic stroke, its effect on the prevalence of carotid atheroma has been studied angiographically. The carotid angiograms of 269 patients with cerebral tumours have been reviewed for evidence of coincidental atheromatous change. The prevalence of signs of arterial disease at the carotid bifurcation proved to be greater amongst patients with an elevated casual blood pressure reading, though the effect was small and confined to subjects over 50 years of age. It is argued that other factors must contribute to the connection between hypertension and the risks of cerebral infarction.