This study retrospectively reviewed 227 patients with ruptured solitary cerebral aneurysm who underwent endovascular embolization with detachable coils between March 1997 and March 2006 to establish the incidence of rebleeding after endovascular treatment for ruptured cerebral aneurysm and identify the risk factors. The site and size of the aneurysm, the interval between treatment and rebleeding, and the outcome were investigated in six of the 227 patients (2.6%) who rebled after treatment. Four patients had large or giant aneurysms located on the internal carotid artery at the origin of the posterior communicating artery. The interval between treatment and rebleeding was less than 1 year in four patients (mean 394.2 days). Two patients died, and the survivors had modified Rankin Scale scores of 0, 2, 3, and 4. Re-embolization was performed in four patients and no further bleeding occurred during the mean follow-up period of 1.9 years after re-treatment. Patients with giant aneurysms of the internal carotid artery are at increased risk for rebleeding. Re-treatment should be considered if there is conventional and/or magnetic resonance angiographic evidence of dome filling. Patients with ruptured cerebral aneurysms must be followed up with diagnostic imaging closely during the first 12 months post-embolization because rebleeding frequently occurs within 1 year after initial treatment. Re-embolization is safe and effective in patients with recurrent hemorrhage from aneurysms previously embolized with detachable coils.