Experimental autoimmune myasthenia gravis (EAMG), which to some extent represents an experimental counterpart of human myasthenia gravis, can be induced by inoculation of various animal species and strains with acetylcholine receptor (AChR). The oral administration of Torpedo AChR to Lewis rats prior to immunization with Torpedo AChR and complete Freund's adjuvant resulted in prevention or delay in the onset of EAMG. Levels of anti-Torpedo AChR antibodies in serum measured by radioimmunoassay were lower in orally tolerant compared to control animals. The model might have a relevance for studying the pathogenesis and immunotherapy of human myasthenia gravis.