This will be prospective, multicentre, observational study. Patients who will initiate treatment with IFNβ-1b (Betaferon) will be followed up to 6 months. Baseline visit (visit 0) i.e. treatment initiation plus four follow-up visits (visits 1-4). For each patient demographics, medical history data, safety parameters, presence of flu-like symptoms and measures to prevent or treat these symptoms will be collected.

Inclusion Criteria:

• Diagnosis of relapsing-remitting multiple sclerosis (RRMS) according to McDonald (2005) criteria
• Age >/= 18 years old
• Treatment MS patients in whom the attending physician has decided to initiate therapy with interferon beta-1b; Betaferon
• Minimum 6 months wash-out period from previous IFNβ
• Written Informed Consent signed

Exclusion Criteria:

• Patients previously treated with any of the disease modifying drugs (DMDs), with the exception of IFNβ therapy which ended at least 6 months earlier
• Patients receiving treatment with IFN beta other than Betaferon (Bayer)

Adult MS patients starting Betaferon therapy