Fragile aneurysm walls and poorly defined necks render the surgical treatment of blood blister–like aneurysms (BBAs) located at nonbranching sites of the supraclinoid internal carotid artery extremely challenging. Such aneurysms have a remarkable tendency to rupture during surgery, especially during the acute period. The authors describe the clinical course of patients with subarachnoid hemorrhage (SAH) caused by BBA rupture and emphasize the value of internal carotid artery trapping combined with high-flow extracranial-intracranial (trapping/EC-IC) bypass during the acute period following SAH. The authors analyzed the clinical records of 7 consecutive female patients with a mean age of 61 years (range 51–77 years) who had been treated between January 2006 and December 2008 at their institute. All 7 patients presented with SAHs corresponding to Fisher Grade 3 and World Federation of Neurosurgical Societies Grades II, III, IV, and V in 3, 1, 2, and 1 patient, respectively. Surgery was postponed in the 3 patients, including 1 in whom the trapping/EC-IC bypass procedure was performed during the chronic period. Two of the 3 patients in whom surgery was postponed experienced preoperative rebleeding, and repeated angiography revealed remarkable enlargement of the aneurysm; both of these patients died before surgery could be performed. The remaining 4 patients underwent trapping/EC-IC bypass during the acute period following SAH. The outcome was excellent (Glasgow Outcome Scale Scores 5), and postoperative angiography demonstrated complete obliteration of the BBA as well as good graft patency in all 5 patients who underwent trapping/EC-IC bypass. Intraoperative bleeding from the BBAs never occurred in any of these 5 patients. Ruptured BBAs were successfully treated with a trapping/EC-IC bypass during the acute SAH period. This surgical strategy for treating BBAs during the acute period might be a promising option for these rare but high-risk lesions.