Objective: To study chronobiological characteristics of ischemic stroke (II) and post stroke cognitive impairment (CI). Material and methods: We examined 80 patients with acute ischemic stroke. The cognitive status, sleep quality, chronobiological parameters and night urinary level of 6-sulfatoxymelatonin were assessed. The clinical observation of the efficacy of melaxen treatment in intensive care unit was performed. Results: The results of the study indicate the significance of social and environmental factors which determine the sleep-wake behavior in the development of pineal dysfunction. The pineal dysfunction probably underlies the development of stroke and accompanied neurodegenerative process. Conclusion: The use of melaxen in hyperacute stroke was associated with better recovery of circadian rhythms and rehabilitation results.