The criteria that characterize restless legs syndrome (RLS) and the differential diagnoses are discussed. Clinical signs include sleep disturbance, involuntary movements in sleep or wakefulness, a normal neurologic examination, a chronic clinical course, and, in some cases, a positive family history. Periodic limb movements during sleep, which also may occur as an isolated finding, may or may not cause frequent arousals or awakenings. Clinical diagnosis of idiopathic or symptomatic forms of RLS can be supported with polysomnography. Treatment of first choice consists of dopaminergic drugs or dopamine agonist followed by opioids or benzodiazepines.