Multiple sclerosis (MS) is a chronic neurological disease, which is known to be more common in UK than many countries. While there are multiple genetic factors affecting risk of developing MS and disease severity within the condition, evidence on the rising worldwide prevalence and the increasing female to male preponderance has focused interest on environmental factors influencing MS risk. Data on several of these factors are reviewed, with particular focus on those such as vitamin intake, smoking and obesity, which may be influenced at a personal and population level by medical advice.