Inclusion Criteria:

- 1.Received alemtuzumab in CAMMS323 or CAMMS324, completed the 2-year study period,
and have not subsequently received disease modifying treatments (other than
glatiramer acetate or interferon beta); or

- 2.Received Rebif® in CAMMS323 or CAMMS324, completed the 2-year study period, and
have not subsequently received alternative disease modifying treatments (other than
glatiramer acetate or another interferon beta); or

- 3.Participated in CAMMS223.

- NOTE: Criteria 1 and 2 above mean that patients who enrolled in CAMMS323 or CAMMS324
but did not complete the 2-year study period or went on to receive non-study drug
DMTs after randomization are not eligible for inclusion in the Extension Study.
Patients who enrolled in CAMMS324 after participation in CAMMS223 must meet criteria
1 or 2 to be eligible for inclusion in the Extension Study.

Exclusion Criteria:

- Any alemtuzumab patient from CAMMS223, CAMMS323, or CAMMS324 who has received
alemtuzumab off-label (ie, outside of one of the prior Genzyme-sponsored studies), or
is participating in any other investigational study, unless approved by Genzyme. In
addition, these patients must be screened for disqualifying safety concerns before
receiving alemtuzumab retreatment.

- Any Rebif® patient from CAMMS223, CAMMS323, or CAMMS324 who meets any of the
following criteria. In addition, these patients must be screened for disqualifying
safety concerns before receiving alemtuzumab treatment. a)Does not wish to receive
alemtuzumab; b) Ongoing participation in any other investigational study, unless
approved by Genzyme; c)Has received alemtuzumab off-label (ie, outside of one of the
prior Genzyme-sponsored studies); d)Known bleeding disorder or therapeutic
anticoagulation; e)Diagnosis of idiopathic thrombocytopenia purpura or other
autoimmune hematologic abnormality; f)History of malignancy, except basal cell skin
carcinoma; g)Intolerance of pulsed corticosteroids, especially a history of steroid
psychosis h)Significant Autoimmune disorder (other than MS); i)Major psychiatric
disorder or epileptic seizures not adequately controlled by treatment; j)Active
infection or high risk for infection k)Unwilling to use a reliable and acceptable
contraceptive method during and for at least 6 months following each alemtuzumab
treatment cycle (fertile patients only).