The present study examined to what extent an acute bout of hypotension influences blood flow in the external carotid artery (ECA) and the corresponding implications for blood flow regulation in the internal carotid artery (ICA). Nine healthy male participants were subject to an abrupt decrease in arterial pressure via the thigh-cuff inflation-deflation technique. Duplex ultrasound was employed to measure beat-to-beat ECA and ICA blood flow. Compared to the baseline normotensive control, acute hypotension resulted in a heterogeneous blood flow response. ICA blood flow initially decreased following cuff-release and then returned quickly to baseline levels. In contrast, the reduction in ECA blood flow persisted for 30 sec following cuff-release. Thus, the contribution of common carotid artery blood flow to the ECA circulation decreased during acute hypotension (-10 ± 4 %, P<0.001). This finding suggests that a preserved reduction in ECA blood flow as well as dynamic cerebral autoregulation likely prevent a further decrease in intracranial blood flow during acute hypotension. The peripheral vasculature of the ECA may thus be considered an important vascular bed for intracranial cerebral blood flow regulation.