Objective: To assess the response to the rotigotine transdermal system (Neupro; Schwarz Pharma Ltd, Monheim, Germany), a nonergolinic dopamine agonist, in patients with early Parkinson disease. Design: Randomized, double-blind, multicenter, placebo-controlled study. Setting: Fifty sites in the United States and Canada. Patients: Two hundred seventy-seven patients with early Parkinson disease. Eligibility was assessed by means of routine clinical and neurological examinations. Patients were randomized 2:1 to receive either rotigotine therapy or placebo. Intervention: Treatment with the rotigotine transdermal system, 2, 4, or 6 mg during 24 hours, for 24 weeks. Main Outcome Measure: Percentage of subjects achieving a 20% response or greater (reduction) as assessed with the Unified Parkinson Disease Rating Scale subtotal (parts II [activities of daily living] and III [motor function]) from baseline to the end of the maintenance phase. Results: Significant differences were observed between the rotigotine-treated and placebo groups for the 20% responder rate (48% for the rotigotine group and 19% for the placebo group; P<.001), least squares mean change in Unified Parkinson Disease Rating Scale subtotal (parts II and III) score (?941 for rotigotine vs ?157 for placebo; P<.001), and percentage changes in Unified Parkinson Disease Rating Scale subtotal (parts II and III) score (?15.1% for rotigotine vs 7.3% for placebo; P<.001). Rotigotine treatment significantly increased the patients' Clinical Global Impression Scale scores (57% for rotigotine vs 30% for placebo; P<.001) and had a positive effect on their quality of life. The most common adverse events were application site reactions, nausea, and somnolence. Twenty-five (14%) of 181 patients in the rotigotine group withdrew from the study because of adverse effects. Conclusion: The rotigotine transdermal system consistently demonstrated statistically significant and clinically relevant efficacy over placebo in patients with early Parkinson disease and was well tolerated. ©2007 American Medical Association. All rights reserved.