This study is primarily designed to evaluate the impact of AVONEX PEN autoinjector on work capacity of participants with multiple sclerosis (MS) starting on this device. This study will also evaluate as secondary endpoints various patient-reported outcomes over the short-term (1 month), including adherence, treatment satisfaction and convenience, and the long-term (12 and 24 months), including adherence, persistence, quality of life (QOL), treatment satisfaction and convenience. It will also assess health resource utilization by MS participants starting on AVONEX PEN autoinjector, as well as overall safety/tolerability, and will correlate all secondary outcomes with the primary (i.e., work capacity).

Key Inclusion Criteria:

• Must be prescribed AVONEX PEN as per local labeling (Product Monograph) and enrolled in MS Alliance (MSA) program
• If being switched from another DMT, must be on this DMT for at least 6 months
• Last DMT the subject is switched from must be injectable
• Must be able to physically demonstrate use of the AVONEX PEN autoinjector device and be able to self-administer the injections
• Must give written informed consent. If required by local law, candidates must also authorize the release and use of protected health information (PHI)
• Must be able to understand and comply with the protocol

Key Exclusion Criteria:

• Female subjects considering becoming pregnant while in the study or who are currently pregnant or breast-feeding
• Current enrollment in any investigational study involving drug, biologic or non-drug therapy
• Participation in other clinical studies within the past 6 months
• Treatment with immunosuppressive regimens (e.g. cyclophosphamide, azathioprine, methotrexate or mitoxantrone) or with intravenous immunoglobulin (IVIg) in the last 6 months
• The most recent DMT the subject is switched from is non-injectable (i.e., oral)
• Other unspecified reasons that, in the opinion of the Investigator or Sponsor, make the subject unsuitable for enrollment

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.

Enrollment will consist of approximately 500 participants who have been prescribed AVONEX PEN in accord with its labeling (Product Monograph). This will include participants who are naïve to disease modifying therapies (DMTs) as well as those who are being switched from another injectable DMT.