AGEING AND MECHANISMS OF BLOOD PRESSURE CONTROL: Ageing is associated with functional and structural alterations to the cardiovascular system. Evidence is accumulating, however, that ageing also determines major changes in the effectiveness of mechanisms involved in blood pressure control and that this represents an important determinant of the cardiovascular changes that can be observed in the elderly. DIFFERENCES SEEN IN ELDERLY SUBJECTS: It has been observed that compared to young subjects, in the elderly (1) baroreceptor control of the heart rate and cardiac function is impaired; (2) baroreceptor modulation of the sympathetic drive to the peripheral circulation is impaired, particularly the speed of reflex adjustments to normal and abnormal stimuli; and (3) cardiopulmonary stretch receptors, which tonically inhibit sympathetic tone, the renal release of renin and vasopressin secretion, are impaired. These three factors may account, at least in part, for the raised blood pressure and sympathetic activity in the elderly. They certainly explain the reduced ability of elderly people to maintain blood pressure and blood volume homeostasis, and their increased blood pressure variability over 24 h. ASSOCIATION WITH HYPERTENSION: All these problems are exacerbated if ageing is associated with hypertension, and are highly relevant to antihypertensive treatment. Care should be taken that any antihypertensive drugs selected for treatment in the elderly do not aggravate these basic homeostatic problems.