Stimulated by the widespread use of head-up tilt testing, transient episodes of neurocardiogenically mediated hypotension and bradycardia have become a well recognized cause of recurrent syncope and near syncope (generally referred to as neurally mediated syncope). On the other hand, a large subgroup of patients was identified, who appeared to have a less severe hypotension and orthostatic intolerance that is characterized by postural tachycardia, exercise intolerance, disabling fatigue, lightheadedness and dizziness. This form of disability has been recognized as postural orthostatic tachycardia syndrome (POTS). While the etiology of POTS is still unclear, a mild form of idiopathic peripheral autonomic neuropathy (partial dysautonomia) or beta-receptor hypersensitivity has been suggested for the pathophysiology of this disorder. A detailed history and physical examination that includes a careful neurologic examination are essential for diagnosis. Head-up tilt testing is often useful as a standardized measure of response to postural change. This review summarizes the history, current knowledge of clinical features, diagnosis and therapeutic strategies.