This is an open label, non randomized, uncontrolled, multicenter, single arm observational study. In this study, the enrolled subjects will be treated with Rebif human serum albumin (HSA)-free formulation (with or without RebiSmart) 44 microgram (mcg), subcutaneous (sc), thrice in a week (tiw) for 24 months.

Inclusion Criteria:

• Male and female subjects aged more than or equal to (>=) 18 years and less than or equal to (<=) 60 years at the time of Rebif introduction
• Subjects diagnosed with RMS according to the revised McDonald criteria (2010)
• Treatment naïve or subjects on other DMDs who will switch to Rebif.
• Subjects will receive 1st Rebif 44 mcg dose after signing informed consent
• Subjects willing and able to provide signed informed consent.

Exclusion Criteria:

• Have any contraindications to treatment with IFN beta-1a sc according to European summary of product characteristics (EU SPC)/prescribed information
• Subjects participating in other clinical studies/trials
• Any female subject of childbearing potential who is not on contraceptives
• Subjects refusal to participate in the study.

Subjects diagnosed with RMS and who are treatment naïve or on other disease modifying drugs (DMDs) will be enrolled into the study.