Background: Although studies report a high prevalence rate of restless legs syndrome (RLS) among patients with multiple sclerosis (PwMS) ranging from 13.3 to 65.1%, little is known about the causes of this relationship. Methods: To ascertain the prevalence, features and impact of RLS among PwMS a nation-wide, multicenter, prospective and a cross-sectional survey, designed to reflect all of the PwMS throughout Turkey, was conducted in 13 centers. Exploring the relationship of the two conditions could possibly contribute to the understanding of the causes of the high and wide-ranging prevalence rates and the pathophysiology of both diseases. Results: Of the 1068 participants 173 (16,2%) found to have RLS [RLS(+)] and 895 (83,8%) did not [RLS(-)]. Among the RLS(+) 173, all but 8 patients (4,6%) were underdiagnosed in terms of RLS. More than half of the patients with RLS had 'severe' or 'very severe' RLS. The onset of RLS was before or synchronous with the onset of MS in about a half of our patients. Conclusion: We conclude that RLS should be meticulously investigated in PwMS and MS can be a direct cause of RLS at least in part of PwMS. Our data about the timing of the onset of MS and RLS, along with the high prevalence of RLS in PwMS suggest that the pathologic changes in the initial phases of MS can possibly trigger RLS symptoms.