In patients with multiple sclerosis (MS) sleep disorders are common, including insomnia, sleep apnea, restless legs syndrome (RLS), narcolepsy, and rapid eye movement (REM)-sleep behavior disorder (RBD). About 40% of patients with MS have insomnia; causes include pain associated with muscle spasms, periodic limb movements, RLS, nocturia, medication effect, and depression. Some recent epidemiological studies have suggested that MS-related RLS should be considered among the symptomatic RLS forms secondary to neurological disorders, and it should be always investigated in patients with MS. Demyelinating lesions in the medullary reticular formation could affect nocturnal respiratory effort, leading to sleep-disordered breathing. However, the prevalence of nocturnal respiratory disturbances in MS is relatively low.Narcoleptic symptoms have long been recognized in patients with MS. Studies published in the first half of the 20th century reported cases of MS associated with sleep attacks termed " narcolepsy" Symptoms of narcolepsy may appear before or after other symptoms of MS.RBD has been described in some patients with MS with plaques in the brainstem. Moreover, the literature over the past three decades has evidenced severe side-effects of antidepressants on REM sleep muscle atonia, and induction of RBD in healthy subjects and in patients with neuropsychiatric disorders. Patients with MS taking such medications may be at increased risk of developing RBD, particularly with increasing age.In conclusion, more than 50% of patients with MS complain of chronic sleep disturbance resulting in daytime somnolence, worsening fatigue, depression, and a lowered pain threshold. An increased clinical awareness and appropriate treatment of sleep disorders in the MS population can improve the quality of life in these patients.