The prevention of cognitive disorders and dementia represents a major challenge in the coming years. Hypertension is one of the principal risk factors for cerebrovascular diseases and is also closely correlated with cognitive decline and dementia. Most longitudinal studies have shown that cognitive functioning is often inversely proportional to blood pressure values measured 15 or 20 years previously. The higher blood pressure was, the poorer cognitive function is. Data from recent therapeutic trials (SYST-EUR, PROGRESS) open the way toward the prevention of dementia (vascular or Alzheimer's type) by antihypertensive treatments. In this context, the effect of antihypertensive treatment on cognitive functions should represent one of the primary criteria of assessment in future morbidity and mortality studies in hypertensive patients.