Antihypertensive treatment may, for the same effect on hypertension, have a very different influence on the cerebral blood flow and the autoregulation curve. For instance, sodium nitroprusside, a potent vasodilator, risks to be poorly tolerated from the cerebral standpoint, when the sympathetic system is not inhibited. Diazoxide has no direct vasodilating effect on the cerebral vessels but, because of its marked hypotensive action must be used in divided doses. Hydralazine, a strong vasodilator, must be avoided in case of cerebral edema and hypertensive encephalopathy. Diuretics and beta-blockers, on a long-term basis, do not significantly modify the cerebral blood flow while alpha-methyl-dopa would increase it and facilitate a return to normal of the autoregulation curve. Captopril has demonstrated experimentally, interesting properties: in anaesthetized rats, it shifts the autoregulation curve to the left, i.e. toward lower pressures and it reduces the autoregulation curve to the left, i.e. toward lower pressures and it reduces the autoregulation limits; in awaken subjects, the decreased lower limit is also observed, explaining the good central tolerance of marked blood pressure reductions; on the contrary, its effects on the upper limit of the plateau are, unquestionably, counterbalanced by the effects of sympathetic stimulation concomitant with sudden blood pressure rises. As for calcium inhibitor, they do not seem to influence the long-term autoregulation of the cerebral flow.