It is a commonly held view that multiple sclerosis (MS) may be an autoimmune disease. Most neurology texts list MS as an autoimmune disease and most texts on autoimmunity point to MS as a prime example of an autoimmune disease of the CNS. This view has influenced research into the pathogenesis of MS to the extent that most published work on MS is based on the assumption that it is correct, ignoring other possibilities, unless they can be put into an autoimmune context. Furthermore, most attempts at treating MS have been with agents that influence the immune system. Some of these agents, such as cytoxan and cyclosporin, are drugs with serious side-effects. Hence, it can be argued that over the years some MS patients have suffered because of the autoimmune hypothesis, although in the end and even today, other MS patients may benefit from it. This article examines some of the evidence in support of autoimmune hypotheses of the pathogenesis of MS. We believe that this examination shows that it has not been proven that MS is an autoimmune disease although it underscores the possibility that it may be so. Although it is still a reasonable hypothesis that MS is an autoimmune disease, it has yet to be proven and it would constitute a serious error of omission not to examine other possibilities.