Background and purpose: Multiple sclerosis (MS) is a common Inflammatory demyelinating disease in central nervous system. So many genetically and environmental factors are involved in forming it. This study has been done in purpose of checking Effective risk factors in Development of multiple sclerosis in Kermanshah. Materials and methods: Current study is an analytical from kind of Case-control study. For doing this, 80 patients with MS and 80 patients without it which were assimilated for age and gender with case group, have been studied. Data gathering tools was self-made questionnaire including demographic features questionnaire and disease risk factors that its validity had been confirmed by Content validity and reliability of Cronbach's alpha test. Obtained data has been analyzed by SPSS 18 and through Descriptive and inferential statistics. Findings: History of accident and trauma to the head and back (p=0.077), history of poultry contact (p=0.07), lack of sunbathing (p=0.151), The menarche age (p=0.01) and having multiple sclerosis in other family members (p=0.000) can increase risk of M.S. Discussion and conclusion: Based on findings, History of accident and trauma to the head and back, history of poultry contact, lack of sunbathing, the menarche age, having multiple sclerosis in other family members and being third child are considered as effective risk factors of disease.