The restless legs syndrome is a condition of unknown aetiology characterized by nocturnal paraesthesiae in the lower limbs, an irreversible tendency to move the limbs, pain in the distribution of the paraesthesiae, and psychiatric disturbances. The syndrome may occur at any age and in either sex and usually runs a course over many years with spontaneous improvements and exacerbations. An association with iron deficiency has been suggested but in most cases no apparent cause has been found, and treatment at present is symptomatic with analgesics and sedatives. The differential diagnosis includes phenothiazine-induced akathisia and meralgia paraesthetica.