Background: Restless legs syndrome (RLS) affects approximately 10-15% of the general population and has deleterious effects on sleep and subsequent daytime performance. The disorder may also give rise to long-term complications such as psychological distress and diminished quality of life. The condition is often unrecognized or misdiagnosed, and the magnitude of the effects of RLS on the sizeable proportion of undiagnosed (and therefore untreated) individuals has not previously been evaluated. Objectives: This study examined the impact of RLS on overall health status, sleep, psychological functioning, work productivity, and daily activities in individuals with diagnosed and in those with undiagnosed (self-reported) RLS. Methods: An internet-based survey was conducted on a multimillion-member panel of US adults. Eligible participants were currently experiencing RLS symptoms as determined using established diagnostic criteria. Participants provided information related to self-reported RLS diagnosis, treatment, symptom frequency and severity, and responses to validated instruments (Medical Outcomes study [MOS] Short Form 12, version 2 [SF-12v2], MOS Sleep Scale, Center for Epidemiological Studies Depression Scale [CES-D], Work Productivity and Activity Impairment - General Health Questionnaire [WPAI-GH] and Work Limitations Questionnaire [WLQ]). Analysis of co-variance (ANCOVA) models were developed to evaluate the relationships among symptom severity, diagnosis status, age, and sex, and the impact of RLS. Results: Participants included 702 adults with RLS symptoms. Means for the SF-12v2 scores (physical component score = 35.6, mental component score = 42.6) were at least 1 standard deviation lower than sex- and age-adjusted general population norms. Participants reported poorer sleep quality scores across each MOS Sleep Scale domain, with differences from published norms of >16 points on 100-point scales, as well as approximately 1 hour less sleep per night on average. A majority (64%) met the cut-off score for depression. Compared with population norms, the sample reported greater limitations in time management, physical demands, mental/interpersonal demands, general work output, and usual activities. Symptom intensity and frequency were shown to be the primary predictors of RLS impact on the various outcomes. Conclusion: These results support previous reports that RLS often goes undiagnosed or misdiagnosed. The results of this survey also suggest that regardless of whether RLS is recognized, the burden of the disorder is substantial, implying a need for improved diagnosis and management of RLS.