Aim: To observe the feature of collateral circulation in patients with severe carotid steno-occlusive disease with the method of digital substraction angiography (DSA). Methods: 150 patients with severe steno-occlusive (≥70%)carotid disease confirmed by DSA were selected from the Department of Neurology, Tiantan Hospital Affiliated to Capital Medical University between October 2003 and December 2004. Aortocranial angiography was performed in arcus aortae +bilateral common carotid artery +bilateral vertebral artery by physicians from Department of Inversive Radiation. Projection was done at two directions of anteroposterior and lateral, displaying extracranial and intracranial artery lesion and collateral compensation fully. Pathological changes of carotid artery and combing with other arteriosis were defined. The anterior communicating artery (ACoA), posterior communicating artery (PCoA), ophthalmic artery (OA), and anterior/posterior leptomeningeal anastomoses (ALep/PLep) were detected. The relationship between collateral circulation and pathogenetic carotid artery was analyzed. Results: In 150 patients with steno-occlusive disease, collaterals appeared in 102 cases (68.0%), and frequency of the presence of ACoA, PCoA, OA, PLep and ALep were 58.8%, 47.1%, 45.1%, 41.2%, 7.8%, respectively. The presence of collaterals (r=0.673, P < 0.001), more than two types of collaterals (compared with only one type) (r=0.273, P=0.014), the presence of ACoA (r=0.311, P=0.005) and OA (r=0.237, P=0.033) increased with the severity of stenosis of the unilateral carotid lesion. The frequency of ACoA was significantly lower with severe intracranial artery stenosis (χ2=6.575, P=0.010). Bilateral carotid lesion was an independent predictor for the presence of PLep (χ2=7.094, P=0.008). Conclusion: ACoA is the major collateral supply artery in patiens with unilateral carotid disease, whereas is damaged with intracranial artery stenosis. The presense of secondary collateral pathways is considered the marker of impaired cerebral hemodynamics.