OBJECTIVE To evaluate the effect of intraoperative angiography in the surgery of brain arteriovenous malformations(AVMs). METHODS Between July 2003 and February 2006, 41 consecutive patients of brain AVMs (18 female and 23 male patients, mean age 34 years) underwent cerebrovascular surgery assisted with intraoperative angiography in our institute. The nidus diameters of AVMs were from 2 cm to 8 cm, including 10 cases of large AVMs (diametre >or=6cm) which accounted for 24%. After intubation was achieved and general anesthesia was administrated, the patient's right femoral artery was catheterized successfully with catheter reaching the intracranial artery during the surgery. When the AVMs were resected, the intraoperative angiography was performed. RESULTS Ten of 41 were patients underwent emergency operation because of acute intracranial hemorrhage without preoperative angiography, who were estimated as AVMs assisted with intraoperative angiography. The nidus had been totally resected in 39 of the 41 (95%) patients confirmed by intraoperative angiography, with 1 patient (2.4%) of motor dominant zone AVMs and 1 patient (2.4%) of posterior fossa AVMs had residual AVMs, which had been noted and resected. There was no operation mortality, no complication attributable to angiography. Intraoperative angiography consumed 25 to 130 minutes with mean time of 53 minutes. CONCLUSIONS Intraoperative angiography can detect the location of small AVMs and unexpected residual AVMs nidus, help surgeons modify technical faults to prevent from re-operation, and decrease complication of cerebrovascular surgery.