Restless legs syndrome (RLS) and periodic limb movements of sleep (PLMS) are common disorders seen in sleep disorder centers. Although RLS in universally thought to cause daytime sleepiness, the role of PLMS in causing sleepiness (or any symptom!) has been more controversial. Recent publications have show that PLMS do not cause either subjective or objective sleepiness, but may be a marker for respiratory effort related arousals. In regards to patients with end-stage renal disease, PLMS may mark mortality. In this same group of patients, gabapentin and normalization of hematocrit may be effective therapies for RLS/PLMS. Melatonin may prove to be an alternative therapy for PLMS.