The incidence of subarachnoid hemorrhage is estimated at 5 to 10 per 100,000 per year. In patients who survive the initial hemorrhage, the repeat hemorrhage rate is 15% to 20% in the first 2 weeks after presentation and is associated with devastating clinical outcomes even graver than the initial rupture. The current options for aneurysm treatment are surgical clipping and, since the mid-1990s, neuroendovascular coil embolization. The former was at one time the gold standard of care, but consistent with the trend in modern medicine toward less-invasive procedures, the latter has steadily gained prominence. Although there is still controversy as to its long-term durability and safety, it is now the preferred procedure. This article describes the procedure's antecedents, rationale, and essential components. Mt Sinai J Med 77:279-285, 2010. (c) 2010 Mount Sinai School of Medicine.