In order to evaluate the variations of the circle of Willis in Korean population digital subtraction angiograms in 200 cases were retrospectively analyzed. There was non-visualiza-tion of the anterior communication artery and the posterior communicating artery in 41 cases and this was the most common type of 4 vessel cerebral angiogram (20.5%) Unilateral or bilateral non-visualization of the posterior commuicating artery was noted in 40 cases (20%) . The fetal origin of the posterior cerebral artery from the internal caroticd artery was seen in 22 cases (11%) In 20 out of 22 cases there were non-visualization of either the anterior communicating or posterior communicating artery. Visualization of the anterior communicating artery was noted in 102 cases (51%) and of the posterior communicating artery in 87 cases (43.5%) Hypoplasia of the anterior cerebral artery was noted in 24 cases (12%) . Non-visualization of the anterior commuicating artery or uni-lateral posterior communicating artery is noted in 16 cases (8%) Non-visualization of the anterior communicating artery was seen in 14 cases (7%) The most common type in appearance of the basilar artery variation was straigh: type (Type 1:51%) and the bifurcation of the basilar artery was most commonly located above the posterior clinoid process of the dorsum sellae (58%) on vertebral angiogram.