We described a patient with occlusion of an internal carotid artery in whom delayed transient ischemic attacks distal to the occlusion alternated with vertebrobasilar attacks. Microembolization through the vertebrobasilar system was emphasized because the middle cerebral artery was filled by the basilar artery through the posterior communicating artery, and one vertebral artery showed important atheromatous emboligenic changes. Other mechanisms appeared improbable because of the type of collateral circulation and absence of other associated emboligenic changes and hemodynamic phenomena.