Myelin basic protein (MBP) is a major protein of central nervous system myelin which can induce experimental autoimmune encephalomyelitis (EAE) in susceptible laboratory animals. The role of T cells in the induction of EAE has been extensively studied, but the antibody response to MBP has not been well characterized. In the present work, we immunized rats with encephalitogenic guinea-pig MBP and mapped autoreactive antibodies binding to peptides in the rat MBP sequence. We studied the responses of the Lewis rat strain, susceptible to EAE, and the responses of the Fischer and Brown-Norway (BN) rats, resistant to EAE. We found that Lewis rats immunized to guinea-pig MBP develop antibodies to a diversity of MBP epitopes with a dominance of MBP peptide p11-30 and peptides in the 71-140 region. Fischer rats showed a similar pattern of antibody specificities, but with higher titers than the Lewis rats. BN rats, in contrast, developed a very low titer of antibodies and lacked a response to p11-30. Thus, there is no clear correlation between the nature of the anti-MBP antibody response and the state of susceptibility or resistance to EAE induction in the different rat strains.