Augmentation constitutes the main complication of long-term dopaminergic treatment in restless legs syndrome (RLS). Although this condition was first described in 1996, and is characterized by an overall increase in severity of RLS symptoms (including earlier onset of symptoms during the day, faster onset of symptoms when at rest, expansion to the upper limbs and trunk, and shorter duration of the treatment effect), precise diagnostic criteria were not established until 2003. These criteria have recently been updated to form a new definition of augmentation based on multicentric studies. The present article reviews our current knowledge on clinical diagnosis, evaluation, pathophysiology, and treatment recommendations for this condition.