Background: Despite being frequently described in patients with end-stage renal disease (ESRD), clinical characteristics and comorbidities in association with restless legs syndrome (RLS) are still to be confirmed. Objectives: The aim of this study was to investigate clinical factors associated with RLS in ESRD patients in hemodialysis. Methods: This is a cross-sectional study of 400 patients on hemodialysis evaluating RLS, clinical features and other sleep abnormalities. Results: Out of 400, 86 patients presented RLS (21.5%; mean age 48.8 +/- 13.8 y), being more frequent in females (p < 0.005). Forty-eight individuals (12% mean age 50.7 +/- 13.1 y) had moderate/severe RLS, 14 reported symptoms prior to hemodialysis, 13 described family history of RLS, and eight described symptoms as disturbing during dialysis. RLS cases showed lower hemoglobin (p < 0.005), poorer quality of sleep (Pittsburgh Sleep Quality Index >5, p = 0.002), higher scores on the Beck Depression Inventory Scale (p < 0.005), greater scores on the Charlson Comorbidity Index (p = 0.01) and the Epworth Sleepiness Scale (p = 0.001) and higher risk of obstructive sleep apnea (OSA; Berlin questionnaire, p = 0.01). Hypertension was more frequent in cases with moderate/severe RLS (p = 0.01) and remained after controlling for the risk of OSA (p = 0.02). Conclusion: In ESRD patients in hemodialysis, RLS is present in 21.5%; 16% report symptoms prior to hemodialysis and a family history of RLS. Symptoms are disturbing during hemodialysis in 9% of cases. RLS is associated with lower hemoglobin, worse sleep quality, excessive daytime sleepiness, depressive symptoms and higher risk of USA. Hypertension is associated with moderate/severe RLS. (C) 2010 Elsevier B.V. All rights reserved.