Inclusion Criteria:

• Be between 18 and 60 years of age.
• Have definite relapsing multiple sclerosis.
• Have had one or more relapses within the prior 12 months.
• Must be in a clinically stable or improving neurological state during the four weeks prior to Study Day 1.
• EDSS score from 0 to 5.5, inclusive
• If female, she must either be post-menopausal or surgically sterilized; or use a hormonal contraceptive, intra uterine device, diaphragm with spermicide, or condom with spermicide, for the duration of the study; and be neither pregnant nor breast-feeding.
• Confirmation that the subject is not pregnant must be established by a negative serum hCG pregnancy test within 7 days of Study Day 1 and a negative urine pregnancy test on Study Day 1. A pregnancy test is not required if the subject is post-menopausal or surgically sterilized.
• Be willing and able to comply with the protocol for the duration of the study
• Voluntarily provide written informed consent and, for USA sites only, a subject authorization under Health Insurance Portability and Accountability Act (HIPAA), prior to any study-related procedure that is not part of normal medical care, with the understanding that consent may be withdrawn by the subject at any time without prejudice to their future medical care.

Exclusion Criteria:

• Have secondary progressive MS or primary progressive MS.
• Prior use of any interferon or glatiramer acetate.
• Have had treatment with oral or systemic corticosteroids or ACTH within 4 weeks of Study Day 1 and within 7 days prior to the Day 1 MRI.
• Have a psychiatric disorder that is unstable or would preclude safe participation in the study.
• Have significant leukopenia (white blood cell count < 0.5 times the lower limit of normal of the central laboratory) within 7 days of Study Day 1.
• Have elevated liver function tests (AST, ALT, alkaline phosphatase > 2.0 times the upper limit of normal (ULN) of the central laboratory, or total bilirubin > 1.5 times the ULN of the central laboratory) within 7 days of Study Day 1 or a history of hepatitis (including infectious or drug-induced).
• Prior cytokine or anti-cytokine therapy within 3 months prior to Study Day 1.
• Prior use of immunomodulatory or immunosuppressive therapy (including but not limited to cyclophosphamide, cyclosporin, methotrexate, azathioprine, linomide, mitoxantrone) within the 12 months prior to Study Day 1.
• Prior use of cladribine or have received total lymphoid irradiation.
• Have allergy or hypersensitivity to human serum albumin, mannitol, glatiramer acetate, natural or recombinant interferon-β, or any other components of the study drugs or gadolinium DTPA.
• Have taken intravenous immunoglobulin or any other investigational drug or taken part in any experimental procedure in the 6 months prior to Study Day 1.
• Presence of systemic disease that might interfere with subject safety, compliance or evaluation of the condition under study (e.g. insulin-dependent diabetes, Lyme disease, clinically significant cardiac disease, HIV, HTLV-1).
• Have had plasma exchange in 3 months prior to Study Day 1.