OBJECTIVES: Idiopathic RLS (Ekbom syndrome) is a sensorimotor disorder that leads to disrupted sleep and poor quality of life. Until now, there have been no internationally approved treatments for this disorder. This study evaluated costs and outcomes resulting from the use of ropinirole in patients with RLS. METHODS: Data were combined from 553 patients enrolled in two matching, pivotal, randomized, 12-week, double-blind, placebo-controlled studies. Patients with moderate-to-severe RLS received ropinirole or placebo, with a maximum allowable dose of 4 mg/day. The primary outcome measure was the International Restless Legs Scale (IRLS). IRLS scores at baseline and study endpoint were mapped to the multi-attribute utility instrument EQ-5D based on expert opinion to derive Quality-Adjusted Life Years (QALYs). Costs of study drug, concomitant neurological medications and cost of adverse events were applied in the model from the perspective of the UK NHS. Lower cost per QALY gained indicates better cost-effectiveness. RESULTS: Based on combined analysis of the entire treatment population over 12 weeks, the QALYs gained for ropinirole and placebo were 0.095 (0.082-0.106) and 0.075 (0.063-0.086), respectively. The mean costs per patient for ropinirole and placebo were £210.52 (£197-£223) and £42.34 (£34-£53), respectively. The incremental QALYs and costs were 0.020 (0.002-0.037) and £168.18 (£150-£187), respectively, resulting in an incremental cost per QALY of £8,405 (£4,557-£41,524). Extrapolation of IRLS scores at trial endpoint to 52 weeks improved the incremental QALY to £6748. For patients reporting more severe sleep disturbance or more severe symptoms at baseline, the cost-effectiveness ratios improved to £5810 (£3,210-£20,177) and £4,587 (£2,881-£10,508), respectively. CONCLUSIONS: In the absence of an active-treatment comparator, this analysis found that treatment of moderate-to-severe RLS with ropinirole is cost-effective compared with placebo using conventional UK cost-effectiveness standards, particularly in patients with more severe sleep disturbance and severe RLS symptoms at baseline.