There were examined peculiarities of "wake-sleep" cycle disorders in 34 patients (32 females, 4 males) aged from 20 to 50 years (average age was 35.7 ± 2.3 years) with relapsing course of mul ti ple sclerosis. We have analyzed the cha rac teristics of course, including age of onset and disease duration, severity and duration of the onset and the following relapses, completeness and duration of clinical remission in time intervals between relapses, the structure of major syndromes, and the severity of neurologic impairment according to Expanded Disability Status Score (EDSS) scale. Based on subjective assessment of severity of sleep disorders there were identifi ed multiple variants of combinations of pre-, intra- and postsomnia. We have used the following special questionnaires: "Survey for sleep problems", "Sleep hygiene Index", "Epworth Sleepiness Scale", Munich Chronotype Questionnaire (MCTQ), Pittsburgh Sleep Quality Index (РSQI), and "Worksheet for characteristics of "wake-sleep" cycle disorders". Pre-somnic disturbances included such indexes as diffi culty in falling asleep (36.5 %), anxiety and/ or fear when going to sleep (33.3 %), need for systematic sleeping pills taking (20.1 %); intra-somnic disturbances included frequent night awakenings (66.7 %), which were combined with superfi cial sleep with a variety of dramatic dreams (23.3 %), shortening of sleep duration (13.3 %), diffi culties when falling asleep after waking up in the night (70.0 %) or total absence of night sleep (33.3 %), parasomnias in the form of nightmares (56.7 %), somnambulism (3.3 %) and somniloquence (16.6 %), night apnea (6.6 %), health impairment in night time — headaches (43.3 %), night sweats (63.3 %), feeling of cold (50.0 %) or heat (53.3 %), rhythmic movements during the sleep (46.7 %); post-somnic — early awakenings without possibility of subsequent sleep (63.0 %), morning and/or daytime sleepiness with lack of energy and feeling of relaxation after night sleep (26.6 %). The probability for occurrence of such disorders seems to be caused by structural demyelinating and degenerative impairments and demonstrates the heterogeneous character of disorders of pathophysiological mechanisms, which initiate the processes of sleep maintenance.