PURPOSE: To evaluate the radiologic findings of carotid-vertebrobasilar anastomosis and associated anomalies. MATERIALS AND METHODS: Thirteen patients with fourteen cases of carotid-vertebrobasilar anastomosis collectedfrom January 1992 to December 1997 were reviewed. Clinical diagnosis refered for cerebral angiography werecerebral infarction(n=3), intracranial hemorrhage(n=2), subarachnoid hemorrhage(n=1), brain tumor(n=3),arteriovenous malformation(n=3) and trigeminal neuralgia(n=1). Cerebral angiograms and clinical symptoms wereretrospectively analyzed. RESULTS: The fourteen carotid-vertebrobasilar anastomsis consisted of eleven cases ofpersistent trigeminal artery and three cases of type I proatantal intersegmental artery. Persistent trigeminalarteries were associated with anterior communicating artery aneurysm(n=1), posterior fossa arteriovenousmalformation(n=2) and persistent trigeminal artery variant(n=5). Type I proatantal intersegmental arteries wereassociated with hypoplastic vertebral arteries(n=2) : only proximal segment in one, and proximal and distalsegments in one case. Only one patient had clinical symptom related to the carotid-vertebrobasilar anastomosiswhich was trigeminal neuralgia. CONCLUSION: Knowledge of the anatomical and radiologic findings ofcarotid-vertebrobasilar anastomosis and associated anomalies will aid in the accurate diagnosis of neurovasculardisease and prevent possible complications during surgical and interventional procedures.