Background Endovascular therapy plays an important role in the treatment of brain arteriovenous malformations (BAVMs).Ethylene vinyl alcohol copolymer (Onyx) is a novel liquid embolic material.This study aimed to summarize our experience of using Onyx for embolization of BAVMs with the focus on embolization technique.Methods From September 2003 to November 2007,115 patients (43 women and 72 men,with a mean age of 29 years)with BAVMs were endovascularly treated with Onyx in our department.The following features of all AVMs were evaluated prior to treatment:type of nidus and shunt,draining veins,and feeding arteries.A total of 196 endovascular procedures were performed.Results The course of endovascular treatment was completed in 88 patients.Additional sessions were planned in 27 patients.Of the 88 patients,total occlusion was obtained in 23 patients (26.1%),near-total (＞80% of the original volume) occlusion was obtained in 35 patients (39.8%) and partial occlusion (＜80% of the original volume) was obtained in 30 patients (34.1%) using embolization as the sole therapeutic technique.Mean volume reduction was 72% (range 30%-100%) in 115 patients.Thirty four patients (38.6%,34/88) underwent radiosurgical treatment.Additional embolization sessions were planned in 27 patients.Complications occurred in 19 patients (16.5%,19/115),leading to death in one patient (mortality 0.9%) and permanent disabling in 3 patients (morbidity 2.6%).Conclusions Onyx was shown to be feasible and safe for embolization of BAVMs.Proper use of the Onyx injection technique largely improved the endovascular treatment of BAVMs.Large AVMs can be adequately reduced in size through the use of additional treatment.