The therapy with Interferon-ß-1b reduces the inflammatory component of multiple sclerosis with positive effects on the disease course. The 8 MUI dose at alternate days is kept constant for years. About 1/3 of patients suspend treatment by three years due to side effects or suspected or accepted ineffectiveness. The main objective of the study is to verify the safety and effectiveness of a cyclical administration (a month of suspension after two of treatment) from the beginning of treatment. There is the possibility that a scheme envisaging therapy free intervals can reduce the onset of negative feedbacks (antagonising the drug therapeutic effect) compared to the standard administration protocol. This might also result in an increase of the drug effectiveness and/or in a longer duration of effectiveness itself. Finally, cyclical administration allows patients to spend actual periods of "therapeutic vacation", with positive psychological effects.

Inclusion Criteria:

• Patients affected by remitting Multiple Sclerosis who had at least a relapse in the last year of the disease.
• Satisfying general clinical conditions according to the researcher. Adequate hepatic function. Capacity to use adequate contraceptive techniques during the study.

Exclusion Criteria:

• Any other disease that might better explain signs and symptoms of the patient.
• Any other disability condition that might interfere with the clinical evolution.
• History of hypersensitivity to natural or recombinant interferon or to human albumin.
• Clinically significant heart diseases and not controlled like dysrhythmias, angina pectoris or congestive heart failure.
• Not adequately controlled epilepsy.
• Inability, according to the examining commission, to grant a complete compliance with the protocol requirements for the whole study.
• Previous therapies modifying the disease course in the last six months.
• Steroid therapies in the last 3 months.
• Pregnancy, lactation, serological positivity to the pregnancy test during the screening period.