One of the dominant T cell epitopes in the acetylcholine receptor (AChR) alpha chain lies within the region 146-162 and has been implicated in the pathogenesis of experimental autoimmune myasthenia gravis (EAMG) in C57BL6 (B6) mice. To directly examine the pathogenic potential of alpha 146-162 in EAMG, B6 mice were primed with AChR in complete Freunds adjuvant (CFA) and subsequently boosted twice with either alpha 146-162 or a control peptide in CFA. Seventy percent of the mice boosted with alpha 146-162 developed muscle weakness characteristic of EAMG, while none of the mice boosted with the control peptide showed any clinical signs of the disease. Thus, the data provided evidence for epitope within AChR alpha 146-162 as one of the EAMG-inducing pathogenic epitopes in B6 mice.