Syncope is most commonly reflex mediated. A sympathetic response to stress is suddenly withdrawn, leading to pronounced vagal tone with hypotension or bradycardia. The hallmark of vasovagal syncope is the occurrence, in a standing patient, of a prodrome of dizziness, nausea, pallor, diaphoresis, and diminished vision. The history should include a search for stimuli (eg, phlebotomy, injury, fear) known to be associated with vasovagal syncope. Carotid sinus hypersensitivity, which is more common in the elderly, is suggested by a history of presyncopal shaving, head-turning, or wearing of a constricting collar. Carotid sinus hypersensitivity should be a considered in patients with syncope that is recurrent despite a negative cardiac workup. In situational syncope, the autonomic reflexive response may result from a specific physical stimulus such as micturition, defecation, or extreme coughing.