Purpose : The aim of the study is to evaluate collateral circulations between external carotid and vertebralarteries in the individuals with no occlusive cerebrovascular diseases. Methods and Materials : Vertebralangiography was performed in 20 patients with subarachnoid hemorrhage, with temporal occlusion of the ipsilateralcommon carotid artery by finger pressure compression. In each case, the following were analyzed in each case :presence or absence of collateral channels ; pattern of collateral channels ; level of anastomosis. Results : Theanastomotic channels were as follows : occipital artery by posterior radicular artery : 15 cases ; ascendingpharyngeal artery by musculospinal artery : 16 cases ; odontoid arterial arch : ten cases ; proximal externalcarotid artery by anterior radicular artery three cases. Conclusion : Awareness of external carotid - vertebralarteries anastomosis as described above can be helpful for effective and safe embolization.