Patency of the internal carotid artery in case of common carotid artery occlusion is usually maintained by a flow of blood from the external carotid into the internal carotid artery. A case where a reversed flow of blood was established from the cerebral circulation into the internal carotid artery and eventually into the external carotid artery is presented. Careful reading of the cerebral views of the standard carotid angiogram allowed detection of a retrograde flow into the internal carotid artery. Surgical exploration confirmed the patency of the internal carotid artery; the occluded common carotid artery was bypassed by a prosthesis, which restored an antegrade flow into the internal carotid artery.