Arterial hypertension is the most important modifiable risk factor for stroke. Up to 50% of all strokes may be attributable to hypertension. The risk of stroke is known to increase in a continuous fashion with a blood pressure (BP) of 115/75 mmHg and higher. Patients with an abnormal circadian BP behavior also appear to be at risk. The benefit of antihypertensive drug therapy has been shown in both primary and secondary prevention of stroke. Generally, a BP target of under 140/90 mmHg is recommended. BP lowering itself appears to be decisive rather than choice of the antihypertensive drug. In the acute phase of ischemic stroke and with some exceptions, BP should only be actively lowered at values over 220/120 mmHg.