This article is focusing on the etiology of the multiple sclerosis (MS). MS is the disease of autoimmune origin, concerning mainly young people with its complicated nature. The course of the degenerative and inflammatory process is variable and unexpected, from featureless to the vast and rapidly progressing nature, leading to the considerable disability. The etiological factors are not still well known. We can distinguish different agents: genetic, immunological and environmental, among them tobacco smoking also. Authors survey the etiopathological basis of the disease.