The development of blood pressure was monitored by the tail-cuff method in normotensive (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP) receiving ethanol (alcohol) in drinking water from weaning (approximately 1 month of age). Alcohol administration over a 3-month period attenuated the development of hypertension in SHRSP and also caused a small reduction of the initial blood pressure rise in WKY. This was accompanied by a reduction of fluid intake and an increase of circulating antidiuretic hormone (arginine vasopressin; AVP). Circulatory volume remained constant. Direct measurement of arterial blood pressure in conscious rats before and after autonomic blockade confirmed the antihypertensive effect of alcohol in SHRSP and indicated that it is at least partly dependent on altered activity of neural mechanisms. Sudden withdrawal of alcohol caused an immediate increase of fluid intake followed by a rise of blood pressure lasting several days in both WKY and SHRSP. This withdrawal hypertension could not be attributed to changes in plasma catecholamines or AVP.