aSAH is a significant cause of morbidity and mortality throughout the world. Although the incidence of aSAH varies widely among populations, perhaps because of genetic dif- ferences, competing burden of disease, and issues of case ascertainment, at the very least, a quarter of patients with aSAH die, and roughly half of survivors are left with some persistent neurological deficit. That said, case-fatality rates appear to be falling, and increasing data suggest that early aneurysm repair, together with aggressive management of complications such as hydrocephalus and delayed cerebral ischemia (DCI), is leading to improved functional outcomes. These improvements underscore the need to continually reassess which interventions provide the greatest benefit to patients. Although large, multicenter, randomized trial data con- firming effectiveness are usually lacking for many of the interventions discussed, the writing group did its best to summarize the strength of the existing data and make prac- tical recommendations that clinicians will find useful in the day-to-day management of aSAH. This review does not discuss the multitude of ongoing studies. Many of these can be found at http://www.strokecenter.org/trials/. The mecha- nism of reviewing the literature, compiling and analyzing the data, and determining the final recommendations to be made is identical to the 2009 version of this guideline.2 The members of the writing group were selected by the AHA to represent the breadth of healthcare professionals who must manage these patients. Experts in each field were screened for important conflicts of interest and then met by telephone to determine subcategories to evaluate. These subcategories included incidence, risk factors, prevention, natural history and outcome, diagnosis, prevention of re- bleeding, surgical and endovascular repair of ruptured aneu- rysms, systems of care, anesthetic management during repair, management of vasospasm and DCI, management of hydro- cephalus, management of seizures, and management of med- ical complications. 