Aim To assess collateral compensative capacity in patients with artery occlusion of internal carotid artery system. Methods In 213 patients with artery occlusion of internal carotid artery system,collateral circulation pathway was measured by transcranial doppler(TCD).Results With extracranial internal carotid artery occlusion,TCD showed ophthalmic artery collateral pathway(OA) in 58%,anterior communicating artery collateral pathway(ACoA) in 93%,and posterior communicating artery collateral pathway(PCoA) in 60% of patients.With distal internal carotid artery occlusion,TCD showed OA in 15%,ACoA in 51%,and PCoA in 61% of patients.In all middle cerebral artery stem occlusion,TCD showed leptomeningeal anastomoses collateral pathway,blood flow velocity compensative acceleration of the lesion side anterior cerebral artery in 91%,blood flow velocity compensative acceleration of the lesion side posterior cerebral artery in 9% of patients.Absent collateral flow was found in 15 patients(7%).The study found 108 patients(55%) with 1 collateral pathway,79 patients(40%) with 2 collateral pathway,and 11 patients(5%) with 3 collateral pathway.Conclusions TCD might further help to know the collateral compensative capacity of patients with artery occlusion of internal carotid artery system.It was suggested that TCD might be an important and objective index in evaluating the treatment effect and the prognosis.