Hypertension has proven to be a major predisposing factor for the development of both vascular and degenerative (Alzheimer's) dementias, either following stroke or gradually through more insidious microcerebrovascular processes. In the latter case the interval between the respective manifestations of hypertension and dementia may vary between a few years and several decades. The temporal relationships may become complicated by the finding that blood pressure tends to fall shortly before the onset of overt Alzheimers' disease. Whether or not timely antihypertensive regimens may delay or even prevent the development of dementias later in life is still an ''educated'' guess, as long there has been no comprehensive trial comparing the potential of the different antihypertensive drug classes in this regard. Until then, the class of dihydropyridine calcium antagonists (exemplified by nitrendipine in the Syst-Eur trial) is the only category having statistically been proven to be of substantial value for prevention of Alzheimer's disease.