The pathophysiology of the restless legs syndrome (RLS) is poorly understood. One index symptom is the urge to move, increasing at night. It is largely accepted that movement in RLS is "involuntary" and that the generators are below the level of the neocortex. Here the authors provide evidence that characteristic leg movements in RLS are preceded by preparatory cortical activation that cannot be attributed to sensory processing or to the expectancy of movement.