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Syncope is a common complaint that is frequently evaluated without identifying a precipitating cause. Gelastic (laughter-induced) syncope is an uncommon and poorly understood condition. We describe 3 patients who experienced loss of consciousness during vigorous laughter. Each patient had an extensive medical evaluation, including a comprehensive history and physical examination, 12-lead electrocardiography, chest radiograph, routine blood analysis, polysomnography, tilt table testing, 2-dimensional transthoracic echocardiography, nuclear or echocardiographic stress testing, and 24-hour Holter monitoring. All 3 patients had an abnormal response to head-up tilt table testing, with either a significant decrease in systolic blood pressure or inappropriate heart rate response on achieving an upright position. These observations together with our review of the literature suggest that gelastic syncope may be a variant of vasodepressor syncope. Knowledge of this condition, its pathophysiology, and potential treatment options may be of value to clinicians when evaluating patients with unexplained loss of consciousness.