Restless legs syndrome (RLS) is a sensorimotor disorder characterized by a distressing urge to move the legs and sometimes other parts of the body. Diagnosis is based on clinical features that may be easily remembered with the mnemonic URGE: Urge to move, Rest induced, Gets better with activity, and Evening and night accentuation. RLS is common, its prevalence increases with age, and women are more frequently affected. The course is chronic with often severe sleep disruption, including periodic leg movements. Differential diagnosis includes disorders of restlessness and leg discomfort. Primary RLS is familial and likely to be genetic. Important causes of secondary RLS are end-stage renal disease, pregnancy, and iron deficiency. Every patient should be checked for iron status with a serum ferritin measurement.