: The work describes three cases of patients at various ages, diagnosed for CNS demyelinating disease. The presence of specific antibodies to B. burgdorferi sensu lato, and findings of B. burgdorferi s.l. DNA, identified in one case as the genospecies B. garinii in the liquor, indicated previous experience with the infection. Presumably, persistence of borrelia in the organism could act as one of the autoimmune process triggers, resulting in the demyelinating disease.