Multiple sclerosis (MS) is an autoimmune disease that affects the central nervous system and is a major cause of disability in able-bodied young people. Recently, the question of the effect of vitamin D on the risk of occurrence and clinical course of MS has been widely discussed. The review presents pathogenesis of this disease and estimated mechanisms of the effect of cholecalciferol on it, current data on the effect of vitamin D levels on the risk of MS, the course and outcome of this disease.