The basic protein is a major structural protein of the central nervous system myelin in which it constitutes 30% of the total protein. T lymphocyte cell lines selected with whole MBP typically recognize only 1-3 immunodominant epitopes (Offner et al., 1987, 1988; Trotter et al., 1987: Bourdctte et al. 1988; McCarron and McFarlin, 1988) and these immunodominant MBP epitopes frequently are cncephalitogenic (Vandenbark et al., 1985b, 1989; Hashim et al., 1991). Thus, the identification of immunodominant MBP epitopes is likely to provide an in vitro method of identifying unrecognized enccphalitogenic epitopes of MBP. Although the cause of multiple sclerosis (MS) is not known, a T cell-mediated autoimmune process has been postulated. Myelin basic protein (MBP) is a potential target antigen because it induces experimental allergic encephalomyelitis (EAE) in susceptible animals. Encephalitogenic epitopes of MBP differ among susceptible strains and correlate with the MHC class II genotype.