The predominant murine T lymphocyte population responding to Tα146-162, the immunodominant epitope in EAMG, expresses the TCRBV 6 gene segment. However, cells expressing other TCRBV gene segments also react with this peptide. In order to more precisely characterize the Tα146-162-specific TCR repertoire, we isolated CD4 h i g h cells from peptide-immunized mice. The majority of CD4 h i g h cells utilized an acidic TCR β chain CDR3 motif regardless of TCRBV gene usage. Analysis of T cell clones demonstrated a fourfold higher avidity of Vβ6+ than non-Vβ6 cells for Tα146-162 indicating that a hierarchy of TCR motifs determines T cell responsiveness in EAMG.