Swift diagnosis and treatment are critical for good outcomes in patients with nontraumatic subarachnoid hemorrhage, which is usually caused by a ruptured aneurysm. This type of stroke often results in death or disability. Rates of misdiagnosis and treatment delays for subarachnoid hemorrhage have improved over the years, but these are still common occurrences. Subarachnoid hemorrhage can be more easily diagnosed in patients who present with severe symptoms, unconsciousness, or with thunderclap headache, which is often accompanied by vomiting. The diagnosis is more elusive in patients who present in good condition, yet these patients have the best chance for good outcome if they are correctly diagnosed at the time of presentation. Physicians should be alert for warning headaches, which are often severe, and headaches that feel different to the patient. Other symptoms may include nausea, vomiting, impaired consciousness, nuchal rigidity, orbital pain, focal neurologic deficits, dysphasia, lightheadedness, and dizziness. The most important risk factors for subarachnoid hemorrhage include cigarette smoking, hypertension, heavy alcohol use, and personal or family history of aneurysm or hemorrhagic stroke. The first step in the diagnostic workup is noncontrast computed tomography of the head. If computed tomography is negative or equivocal, a lumbar puncture should be performed. Subsequent imaging may include computed tomographic angiography, catheter angiography, and magnetic resonance angiography.