Relapsing experimental autoimmune encephalomyelitis (EAE) was induced in Lewis rats by intraperitoneal immunization with guinea pig whole central nervous system tissue. Basic protein (BP)-specific T cell lines selected from rats with relapsing EAE proliferated in response to BP, the 44-89 peptidase fragment of BP and the synthetic peptide, S72-89, as did lines selected from rats with non-relapsing EAE induced by immunization with guinea pig BP. BP-specific T cell lines selected from rats with relapsing EAE transferred acute but not relapsing EAE. BP-specific T cell lines selected from Lewis rats with relapsing EAE appear not to differ from those selected from rats with non-relapsing EAE.