We report here 3 cases of major artery injury during surgery for cerebral aneurysms. Case 1 was 63-year-old female with unruptured aneurysms on the right distal anterior cerebral artery (D-ACA) and right middle cerebral artery. Upon release of the temporary clip on the proximal anterior cerebral artery after clipping of the D-ACA aneurysmal neck, the aneurysm was avulsed together with the clip on the aneurysmal neck by the clip applier. The arterial defect was closed with 2 stitches and clipped to maintain the vessel structure. Case 2 was 49-year-old female with ruptured left anterior wall aneurysm of the internal carotid artery (ICA). When a clip was placed at the aneurysm covered with blood clots, the aneurysm ruptured at its base and a large hole appeared in the wall of the artery. The defect in the wall was closed with 3 stitches and reinforced with 2 clips parallel to the ICA axis. Case 3 was 52-year-old male with left paraclinoid unruptured aneurysm. For the purpose of proximal control, the cervical ICA was exposed and prepared for temporary ligation by silicon rubber tape. During the clipping procedure for the aneurysm, the ICA was temporarily ligated many times, resulting in wall dissection at the ligated portion. After the blood flow was stopped, the ICA was incised and the clots in the wall were removed. The dissected intima was cut off and 3 tacking sutures were placed on each side of the proximal and distal ends of the dissection. Injury to a major arterial trunk rarely occurs during surgery for cerebral aneurysms. Even so, microsurgical instruments for stitching in a deep field should be prepared for these sudden events for successful surgery.