Restless legs syndrome (RLS) and periodic limb movement disorder (PLMD) are thought to center around a genetically mediated sensitivity to iron insufficiency. Previous studies have shown the effectiveness of short-term iron therapy in children with low iron storage. Little is known, however, about long-term iron treatment in children with RLS and PLMD. Therefore, we performed this study to assess the long-term effect of iron therapy in children with RLS and PLMD.