PURPOSE: The aim of the study is to evaluate collateral circulations between external carotid and vertebral arteries in the individuals with no occlusive cerebro vascular diseases. METHODS AND MATERIALS: Vertebral angiography was performed in 20 patients with subarachnoid hemorrhage, with temporal occlusion of the ipsilateral common 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: The anastomotic channels were as follows : occipital artery by posterior radicular artery : 15 cases ; ascending pharyngeal artery by musculospinal artery : 16 cases ; odontoid arterial arch : ten cases ; proximal external carotid artery by anterior radicular artery three cases. CONCLUSION: Awareness of external carotid - vertebral arteries anastomosis as described above can be helpful for effective and safe embolization.