Introduction: lifestyle plays the most important role in the prevalence and distribution of chronic diseases. One of the chronic diseases is Multiple Sclerosis (MS) which has shown an upward trend in the world and in Iran over the last years. Therefore, the present study was designed to survey the effect of lifestyle on Multiple sclerosis prevalence.   Material and Method: This ecological study was conducted in Iran. Main variables of lifestyle included cigarette smoking, physical activity, Body Mass Index (BMI), and fruits and vegetables intake these data along with the data about MS were obtained from the Ministry of Health, Treatment and Medical Education of Iran. Linear regression was used for statistical analysis and SPSS software (version 16) was used to analyze the data.   Results: There was a significant correlation between cigarette smoking index in males and females and the prevalence of MS (P=0.001 and 0.04, respectively) but there was no correlation about the other lifestyle factors with MS prevalence. Also, t here was no correlation between latitude and sunlight exposure and MS prevalence.   Conclusion: This study indicated an increasingly upward trend of MS prevalence in Iran. Moreover the effect of cigarette smoking on MS prevalence became more apparent. Effect of other factors on MS prevalence needs further studies.