The objective of this study was to investigate the long-term efficacy of ropinirole in patients with restless legs syndrome (RLS) and to assess the potential for relapse after the discontinuation of active treatment. Patients with primary RLS (n = 202) received single-blind ropinirole for 24 weeks. Patients meeting treatment continuation criteria were randomized to double-blind treatment with ropinirole or placebo for a further 12 weeks. The primary efficacy variable was the proportion of patients relapsing during double-blind treatment. Additional efficacy measures included time to relapse, withdrawals due to lack of efficacy, improvement on the Clinical Global Impression-Improvement (CGI-I) scale, change in International Restless Legs Scale (IRLS) score during double-blind treatment, and changes in sleep and quality of life (QoL) parameters. Significantly fewer patients relapsed on ropinirole than on placebo (32.6% vs. 57.8%; P = 0.0156). Time to relapse was longer with ropinirole and more patients withdrew due to lack of efficacy with placebo. Patients showed improvements in IRLS and CGI-I scores, sleep and QoL parameters with single-blind ropinirole, which were better maintained when ropinirole was continued during the double-blind phase, but reduced with placebo. Ropinirole was well tolerated; adverse events were typical for dopamine agonists. Ropinirole was highly effective and well tolerated in the long-term management of RLS, with pharmacological effect over 36 weeks.