Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). Most evidence supports the autoimmune pathogenesis of the disease. According to this hypothesis, the activation of autoreactive T-cells is a central event in the development of autoimmune response in MS. We examined molecular events involved in the initiation of autoimmune response in MS. Recent studies in our laboratory have reported an unexpectedly high degree of T-cell receptor (TCR) degeneracy and molecular mimicry as a frequent phenomenon that might play a role in the initiation of autoimmune response in MS. This paper provides insights into the physiologic and pathologic role of autoreactive T-cells, and characterizes structurally and functionally the specific targets for new therapies of MS.