Restless Leg Syndrome (RLS) is a common neuropathic disorder in patients with end stage renal disease (ESRD). Study Design: Because micronutrient depletion has been associated with RLS in ESRD and because the vitamin biotin is dialyzable, the investigators examined the relationship between biotin status and RLS in ESRD. Objectives: To assess the prevalence of biotin deficiency in those with and without RLS (Study 1) and to determine the effect of biotin supplementation on RLS symptoms (Study 2) in patients receiving chronic dialysis due to ESRD.