The aim of this retrospective study is to review and describe safety, tolerability and efficacy of Rebif® (subcutaneous interferon [IFN]-beta-1a) in children and adolescents, using information already recorded in medical records. The study duration is 13 July 2010 (first data collected) to 13 July 2011 (last data collected). In this study, Data of the subjects evaluated between 1997 and 2009 was observed.