The primary objective is to evaluate the safety and tolerability of natalizumab (BG00002, Tysabri®) in the study population (Russian participants with relapsing remitting multiple sclerosis). The secondary objectives are to look at evaluation of severity of relapse, hospitalization and steroid use requirement; Expanded Disability Status Scale (EDSS), functional tests, quality of life self-assessment questionnaires including the short form health survey self-assessment questionnaire (SF-36) and multiple sclerosis impact scale 29 (MSIS-29), evidence of MRI disease activity, participants free of disease activity (clinical activity and/MRI activity) and anti JC Virus (JCV) antibody evaluation.