Syncope is a frequent diagnostic and therapeutic challenge for emergency room physicians, primary care providers, cardiologists and electrophysiologists. Syncope accounts for 3 % of emergency room visits and 6 % of all hospital admissions, with a lifetime incidence of nearly 40 %. Syncope is derived from the Greek word synkopē, which means “to cut short” or “to interrupt”. Syncope is defined by transient loss of consciousness due to global cerebral hypoperfusion. It is characterized by rapid onset, short duration, and spontaneous complete recovery. Understanding the pathophysiological basis for the syncopal episode is the most useful tool for etiology-based treatment and risk assessment. The classification of syncope based on pathophysiology is discussed.