Multiple sclerosis (sclerosis muliplex, SM) is a chronic inflammatory-demyelinating disease of the central nervous system with the etiology not yet completely known. It begins in most cases between the 20th and 30th year of life. It occurs mainly in the caucasian race, more often in women. It is a disease with multi-factor pathogenesis, in which genetic, immunopathological and environmental factors intertwine in a complex manner. The authors present the current state of knowledge on the role of environmental factors in multiple sclerosis pathogenesis.