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 collected from January 1992 to December 1997 were reviewed. Clinical diagnosis refered for cerebral angiography were cerebral 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 were retrospectively analyzed. Results : The fourteen carotid-vertebrobasilar anastomosis consisted of eleven cases of persistent trigeminal artery and three cases of type I proatantal intersegmental artery. Persistent trigeminal arteries were associated with anterior communicating artery aneurysm(n=1), posterior fossa arteriovenous malformation(n=2) and persistent trigeminal artery variant(n=5). Type I proatantal intersegmental arteries were associated with hypoplastic vertebral arteries(n=2): only proximal segment in one, and proximal and distal segments in one case. Only one patient had clinical symptom related to the carotid-vertebrobasilar anastomosis which was trigeminal neuralgia. Conclusion : Knowledge of the anatomical and radiologic findings of carotid-vertebrobasilar anastomosis and associated anomalies will aid in the accurate diagnosis of neurovascular disease and prevent possible complications during surgical and interventional procedures.