A panel of 90 myelin basic protein (MBP)‐specific T‐cell lines were derived from peripheral blood of eight patients with multiple sclerosis and four normal subjects. The precursor frequency of MBP‐reactive T cells in peripheral blood mononuclear cells ranged from 10⁻⁷ to 9 × 10⁻⁷ (mean, 6.7 × 10⁻⁷) in the group of patients with multiple sclerosis and from 0.5 × 10⁻⁷ to 9.8 × 10⁻⁷ (mean, 5.6 × 10⁻⁷) in the control subjects. This difference between the two groups was not statistically significant (p > 0.1). These T‐cell lines expressed exclusively CD3+CD4+CD8‐ phenotypes and were restricted predominantly by HLA‐DR molecules. When tested with fragments and synthetic peptides of human MBP, these MBP‐specific T‐cell lines (45 lines for each group) displayed a limited heterogeneous pattern with a biased recognition to peptide 84‐102 and the C‐terminal peptide 149‐171. The reactivity to the 84‐102 region of MBP was associated with the HLA‐DR2, DRw15 (DRwl5,2) haplotype, whereas the recognition to peptide 149‐171 did not correlate with a particular HLA‐DR allele(s). Furthermore, the majority of T‐cell lines (>75%) were found to exhibit substantial cytotoxic activity against MBP‐coated target cells, but showing no significant difference between these two groups. This MBP‐dependent Cytotoxicity was not associated with epitope specificities of the T‐cell lines tested.