Multiple sclerosis (MS) is a demyelinating disorder of the central nervous system (CNS) but the causes have not been defined. The disease process appears to involve interplay between environmental factors and certain susceptibility genes. It is likely that the identification of the exact etiological mechanisms will permit the development of preventive and curative treatments. Evaluation of several diseases found to be more often associated than by chance alone may reveal clues to the etiology of those disorders. An association between MS and inflammatory bowel diseases (IBD) was suggested by the observation of an increased incidence of IBD among MS patients. A problem in the interpretation of the data rests, in part, with the observation that abnormal findings in brain magnetic resonance imaging (MRI) may be reported as MS in IBD patients. Defining the limits between incidental MRI findings and findings compatible with MS has resulted in further exploration of this possible association.