Immunogenicity and Safety Study of Serum-Free Avonex

Inclusion Criteria: * Must have a diagnosis of relapsing/remitting MS as defined by McDonald, et al15; criteria numbers 1-4. * Must have an expanded disability status scale (EDSS) score between 0 and 5.5, inclusive. * Must be able to understand and comply with the protocol. Exclusion Criteria: * Has experienced a relapse within 2 months prior to Day 1. Relapses are defined as new or recurrent neurologic symptoms not associated with fever or infection, lasting at least 48 hours, and accompanied by new objective neurological findings upon examination by the investigator. * History of any significant cardiac, endocrinologic, hematologic, hepatic, immunologic, metabolic, urologic, pulmonary, neurologic, dermatologic, psychiatric, renal, and/or other major disease that would preclude therapy with interferon beta. * Abnormal screening or baseline blood tests determined to be clinically significant by the investigator * History of a seizure within 3 months prior to Day 1. * History of suicidal ideation within 3 months prior to Day 1 or an episode of severe depression within 3 months prior to Day 1. * Known allergy to natural rubber latex. Other inclusion and exclusion criteria apply as per protocol