This randomized, double-blinded, placebo-controlled trial (NCT00135993) assessed efficacy and safety of the dopamine agonist rotigotine in the treatment of idiopathic restless legs syndrome (RLS) over a 6-month maintenance period. A total of 505 eligible participants with moderate to severe RLS (IRLS sum score >or= 15) were randomly assigned to five groups to receive either placebo or rotigotine (0.5, 1, 2, or 3 mg/24 hr) delivered by once-daily transdermal patch (fixed-dose regimen). The two co-primary efficacy parameters decreased from baseline to end of maintenance in IRLS sum score and in clinical global impressions (CGI-1) score. On both primary measures, 2 and 3 mg/24 hr rotigotine was superior to placebo (P < 0.001). Adjusted treatment differences to placebo for the IRLS sum score were -4.5 (95% CI: -6.9, -2.2) for 2 mg/24 hr rotigotine, -5.2 (95% CI: -7.5, -2.9) for 3 mg/24 hr rotigotine, and for CGI item 1 -0.65 (95% CI: -1.0, -0.3) and -0.9 (95% CI: -1.3, -0.5) for the 2 and 3 mg/24 hr doses, respectively. Skin reactions (27%) and known dopaminergic side effects such as nausea (18.1%) and headache (11.6%) were mostly mild or moderate in rotigotine subjects. Rotigotine transdermal patches releasing 2 to 3 mg/24 hr significantly reduced the severity of RLS symptoms. Treatment efficacy was maintained throughout the 6-month double-blind period.