The European Charcot Foundation, in its goal to support and stimulate information on new developments in Multiple Sclerosis (MS), presents an up-to-date volume on the relation of genes and viruses to MS. That genetic susceptibility might play an important role in the way the immunological system handles viral infection, or in the way brain cells react to viral invasion, has in recent years been extensively studied. Experimental evidence from animals makes a viral oligodendrocytopathy a certainty, and this in itself opens the perspective of such a disease in human beings. New insights in MS-pathology indicate that in a number of MS-patients an oligodendrocytopathy is paramount, however, proof that this may be virus-induced is absent so far. This book discusses viral activities in the brain of Multiple Sclerosis patients, genetic backgrounds in MS and their role in brain response to viral infections, and provides evidence for viral pathogenesis of Multiple Sclerosis.