The aim of this study is the assessment of the efficacy and safety of Cinnaferon (Interferon beta-1- b, Subcutaneous, every other day) in patients with Relapsing- Remitting multiple sclerosis, over a 24-month period. This study will be undertaken in one center in Iran (Tehran, Sina Hospital). Relapsing-Remitting Multiple Sclerosis patients aged between 18-50 years and Expanded Disability Status Score (EDSS) between 0-5.5 will be included. These individuals are randomly divided into two groups. The intervention group receives Cinnaferon (250µgr / 8 mIU / day, subcutaneous, every other day) and the control group receives Betaferon (250µgr / 8 mIU / day, subcutaneous, every other day). To avoid any prejudgment, both patients group and physicians will not informed about the type of prescribed medication (Cinnaferon or Betaferon) , but they will be informed about chemical formulation of the drug as beta interferon1-b. The patients in both groups will be evaluated and compared by the number of relapses, the change in EDSS score, MRI findings and neutralizing antibodies. In addition, side effects will be systematically recorded for both treatments.