We assessed the risk of multiple sclerosis (MS) associated with a series of putative risk factors. We studied 140 patients (90 women) with MS (mean age, 42.1 years; SD= 10.2 years; disease duration, 10.9 years, SD= 7.5 years) and 131 sex-and age-matched controls. Using a structured questionnaire, we collected information related to demographic data, socio-economic status, education, ethnicity, changes of domiciles, migration, occupation, environmental, nutritional and hormonal factors, exposure to various bacterial and viral agents, vaccinations, and family history of diseases. In multiple logistic regression analysis, we found independent risk factors of MS to be: familiarity for MS (OR= 12.1; 95% CI, 1.3-110.7), autoimmune diseases (OR= 3.8; 95% CI, 2.0-7.1) and migraine (OR= 8.7; 95% CI, 1.0-75.4); comorbidity with autoimmune disease (OR= 6.8; 95% CI, 1.4-32.0) and migraine (OR= 13.5; 95% CI, 1.5-116.6); and vaccination against measles (OR= 92.2; 95%, 12.1-700.2). Familial susceptibility to MS, autoimmune diseases and migraine, and vaccination to measles are associated with an increased risk of MS. The data collected in this study are confirmatory and support the hypothesis that etiology of MS constitutes the effect of interplay between genetic and environmental risk factors. However, the relatively small number of cases and controls prevents firm conclusions.