Epidemiological studies of stroke have been consistent in identifying hypertension as the major single precursor of cerebrovascular disease. It is an equally important precursor of thromboembolic and major haemorrhagic stroke. Whereas young persons with mild hypertension are at increased risk of myocardial infarction, with increasing age and at higher blood pressure levels stroke becomes relatively more important. All the major intervention studies using antihypertensive drugs have shown a decline in fatal and non-fatal stroke in the treated group. In the five placebo-controlled studies where the average treatment placebo difference was 6 mmHg, the mean reduction in fatal stroke was 47% and non-fatal stroke was 51%. Evidence from the Mayo Clinic indicates a substantial decline in stroke incidence as well as stroke mortality. The period of this decline corresponds to the widespread introduction of antihypertensive therapy and it is tempting to speculate that the campaigns to reduce blood pressure are largely responsible for this decline.