MRI is very sensitive in showing MS lesions throughout the CNS. Using MRI for diagnostic purposes, however useful, is a complex issue because of limited specificity of findings and a variety of options as to when, how, and which patients to examine. Comparability of data and a common view regarding the impact of MRI are needed. Following a review of the typical appearance and pattern of MS lesions including differential diagnostic considerations, we suggest economic MRI examination protocols for the brain and spine. Recommendations for referral to MRI consider the need to avoid misdiagnosis and the probability of detecting findings of diagnostic relevance. We also suggest MRI classes of evidence for MS to determine the diagnostic weight of findings and their incorporation into the clinical evaluation. These proposals should help to optimize and standardize the use of MRI in the diagnosis of MS.