Objective To analyze the risk of embolization of brain AVMs,study the angioarchitectural factors affecting the difference of embolization level,and to establish the angioarchitecture grading system for embolization of brain AVMs.Methods The clinical data,angioarchitectural features, embolism complication and embolism level were retrospectively analyzed.Multivariate statistical analysis was performed to determine if any of the variables was predictive of a poor outcome of embolization(death or permanent neurological deficit),and if any of the variables was predictive of the percentage obliteration achieved by embolization.Based on the above results,we established the angioarchitecture grading system.Results Endovascular procedures for embolization were performed 324 times in 189 patients during an 11-year period.Embolization was performed using N-butyl cyanoacrylate.In those patients,3(1.6%) died and 5(2.6%)had a permanent neurological deficit as a result of the embolization.The AVMs were given a score from 0 to 5 based on the size,number of the first grade feeding artery,and number of the second grade feeding artery.The assigned scores were as follows:nidus size(AVF=0,