1. Although it is well established that hypertension is the main risk factor for stroke, the complexity of cerebrovascular problems related to hypertension is not generally appreciated. 2. Hypertension can cause stroke through many mechanisms. A high intraluminal pressure will lead to extensive alteration in endothelium and smooth muscle function in intracerebral arteries. The increased stress on the endothelium can increase permeability over the blood-brain barrier and local or multifocal brain oedema. Endothelial damage and altered blood cell-endothelium interaction can lead to local thrombi formation and ischaemic lesions. Fibrinoid necrosis can cause lacunar infarcts through focal stenosis and occlusions. Degenerative changes in smooth muscle cells and endothelium predisposes for intracerebral haemorrhages. Furthermore, hypertension accelerates the arteriosclerotic process, thus increasing the likelihood for cerebral lesions related to stenosis and embolism originating from large extracranial vessels, the aortic arch and from the heart. 3. Adaptive structural changes in the resistance vessels, while having the positive effect of reducing the vessel wall tension, have the negative consequence of increased peripheral vascular resistance that may compromise the collateral circulation and enhance the risk for ischaemic events in connection with episodes of hypotension or distal to a stenosis. 4. Hypertension is clearly a risk factor for vascular dementia. All the mechanisms referred to above may be important.