Hypertension is the most important modifiable risk factor for stroke. The risk of stroke increases directly in proportion to systolic and diastolic blood pressure, and lowering blood pressure can reduce the risk of a first stroke by up to 40%. Current evidence suggests that it is safe and effective to lower blood pressure with an ACE inhibitor and a thiazide diuretic in patients with established cerebrovascular disease. The reduction in subsequent stroke is present both in hypertensive and non-hypertensive patients and is most likely to be related directly to the blood pressure- lowering effect. Ongoing studies will help to determine whether other classes of drugs, such as the angiotensin receptor blockers, are also safe and effective in the secondary prevention of stroke, and whether blood pressure should be lowered in the first few days after a major stroke.