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.