The primary objective of the study is to estimate the annualized relapse rate (ARR) in participants with Relapsing Remitting Multiple Sclerosis (RRMS) who are treated with dimethyl fumarate (DMF) over a 12-month period.

The secondary objectives of this study in this population are to assess the impact of DMF over a 12-month period on participants -reported health-related quality of life (HRQoL) outcomes, additional clinical effectiveness outcomes, and health economics-related outcomes, and to characterize participants-reported adherence to DMF.

Key Inclusion Criteria:

• Have a diagnosis of Relapsing-Remitting Multiple Sclerosis (RRMS) and satisfy the approved therapeutic indication for DMF (per the local DMF product information).
• Must be naïve to DMF, Fumaderm®, and other compounded fumarates, and to MS therapies that are primarily prescribed second-line (e.g., natalizumab, fingolimod) and to alemtuzumab.
• Have a recent complete blood count (CBC) that does not preclude the subject's participation in the study, in the judgment of the Investigator.

Key Exclusion Criteria:

• Are unwilling or unable to comply with study requirements, or are deemed unsuitable for study participation as determined by the Investigator.
• Have major comorbid conditions that preclude participation in the study, as determined by the Investigator.
• Are pregnant, unless DMF is clearly needed and the potential benefit of DMF to the subjects justifies the potential risk to the fetus, in the judgment of the Investigator (in all countries except Austria). In Austria, pregnant subjects are excluded from participation in the study.
• Are women of childbearing potential and are not using appropriate contraception (per the local DMF product information) as determined by the Investigator.
• Women who are breastfeeding may be excluded (per the local DMF product information) at the discretion of the Investigator.
• Have previously received or are receiving treatment with MS therapies primarily used second-line (e.g., natalizumab, fingolimod) or alemtuzumab, or are currently receiving and planning to continue on other disease-modifying therapies for RRMS.
• Are hypersensitive to the active ingredient in the DMF drug product (i.e., DMF) or to any of the excipients listed in the local DMF product information.
• Current enrollment in any clinical trial except for the Biogen Idec DMF Pregnancy Exposure Registry or other studies that, according to the study Medical Director, do not conflict with this study (e.g., health economics studies or local registries).

Other protocol-defined inclusion/exclusion criteria may apply.