This chapter covers the diagnosis and management of spontaneous subarachnoid hemorrhage due to rupture of intracranial aneurysms. At the end of the chapter we also discuss unruptured intracranial aneurysms. Much SAH management is not based on good-quality evidence. Much of what is recommended here comes from published practice guidelines and what is commonly practiced. Options for therapy might be limited by the availability and experience of persons performing surgery, endovascular therapy, and neurointensive care.