Syncope and near-syncope are great diagnostic challenges in medicine. On the one hand, the symptom may result from a benign condition and pose little or no threat to health other than that related to falling. On the other hand, syncope or near-syncope can be the manifestation of a serious underlying condition that poses an imminent threat to life. Patients with a cardiac cause of syncope are at far greater risk of dying in the first year after an episode of syncope or near-syncope than individuals with a noncardiac cause. A cardiac cause of syncope should be considered in every patient with syncope or near-syncope, but it is particularly common in older patients or in patients with known structural heart disease, arrhythmia, or certain electrocardiographic abnormalities. Although many diagnostic tests may be helpful in the evaluation of syncope and near-syncope, the history, physical examination, and electrocardiogram pinpoint the cause in many circumstances.