Objectives: effect of high dose vitamin D3 intake vs placebo on interleukin-10, 17 and quality of life in Multiple Sclerosis patients Design: randomized clinical trial Study groups: intervention and placebo group Phase:1 phase, 3 months Sample size:40 for each group Blinding: The patient and laboratory staff where the blood samples are obtained remain blinded throughout the study. Randomization: Randomization is performed by selection from sealed envelopes. Setting and conduct: After giving informed consent, eligible patients are randomized to one of two groups. The study physician gives medication or placebo to the participant according to randomization and allocation. Participants including major eligibility criteria: Inclusion criteria: a definite diagnosis of Relapsing-remitting MS (RRMS) according to Mc Donald criteria؛ age 18 to 55 years؛ EDSS (Expanded Disability Status Scale) score of less than 4؛ no relapse 30 days before inclusion؛ negative β-HCG test for women in child bearing age. Exclusion criteria: pregnancy؛ lactation؛ any other disease than MS؛ receiving>4000IU/d vitamin D؛ past history of renal or hepatic disease؛ relapse during the study؛ received corticosteroids in the previous 30 days؛ Calcium (Ca)>11mg/dl؛ Aspartate Transaminase(AST) or Alanine Transaminase(ALT)>3 times normal values؛ alkaline phosphatase (ALP)>2.5 times normal values. Intervention:One group receives 50,000IU vitamin D every five days (Vitamin D Pearl, 50,000IU, Zahravi pharmaceutical Co., Tabriz, Iran). The other group receives placebo. main outcome measures: primary outcome variables: Interleukin 10, 17 secondary outcome variables: quality of life