In order to evaluate the vriations of the circle of Willis in korean population, digital subtraction angiograms in 200 cases were retrospectively analyzed. There was non-visualization of the anterior communicating artery and the posterior communicating artery in 41 cases and this was the most common type or 4 vessel cerebralangiogram(20.5%). Unilateral or bilateral non-visualization of the posterior communicating artery was noted in 40cases (20%). The fetal origin of the posterior cerebral artery from the internal carotid artery was seen in 22cases (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 24cases (12%). Non-visualization of the anterior communicating artery or unilateral posterior communicating arteryis 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 straight type (Type 1:51%) and bifurcation ofthe basilar artery was most commonly located above the posterior clinoid process of the dorsum sellae (58%) on vertebral angiogram.