Women are less susceptible to the cerebrovascular complications of hypertension, such as a stroke and vascular dementia. The mechanism of such protection may be related to a reduced vulnerability of females to the cerebrovascular actions of hypertension. To test this hypothesis we used a model of hypertension based on infusion of angiotensin II (AngII), an octapeptide that plays a key role in hypertension and produces cerebrovascular dysregulation. Cerebral blood flow (CBF) was monitored by laser-Doppler flowmetry in anesthetized (urethane-chloralose) C57BL/6J male and female mice equipped with a cranial window. AngII administration (0.25 µg/Kg/min; i.v. x 30-45 min) elevated arterial pressure equally in both sexes, but attenuated the CBF increase induced by whisker stimulation or by the endothelium-dependent vasodilator acetylcholine (ACh) in male, but not in female mice. Administration of AngII for 7 days (2.74 mg/kg/day) using osmotic minipumps also attenuated these cerebrovascular responses in male, but not female mice. The reduced susceptibility to the effect of AngII in females was abolished by ovariectomy and reinstated by estrogen administration to ovariectomized mice. Administration of estrogen to male mice abolished the AngII-induced attenuation of CBF responses. We conclude that female mice are less susceptible to the cerebrovascular dysregulation induced by AngII, an effect related to estrogen. Such protection from the deleterious cerebrovascular effects of hypertension may play a role in the reduced vulnerability to the cerebrovascular complications of hypertension observed in women.