Five hundred patients will be enrolled in the prospective portion of the study, all of whom will receive AVONEX. Patients will join the study by signing the attached Informed Consent Form (Appendix 1) at their doctor's office at the time of prescription. Innomar will provide the drug to approximately 40 new patients per month, so it will take about twelve to fourteen months to enroll all of the study subjects, assuming that all agree to participate. Once the recruitment period is over, it will take another 22 months to complete the study to the 22-months point for the last subject.