The sensitivity of stimulated single‐fiber electromyography in the detection of early abnormalities in neuromuscular transmission in experimental autoimmune myasthenia gravis (EAMG) was tested. Increased jitter and blocking were seen up to 3 weeks before clinical illness or decrement developed. Stimulation at 10 Hz appeared more sensitive in detection of abnormalities than stimulation at 3 or 5 Hz. Jitter values did not correlate with anti‐Torpedo acetylcholine receptor (AChR), nor with anti‐rat AChR antibody titer. No correlation was found between jitter and AChR loss or AChR‐antibody complexes in muscle. It is concluded that, in addition to AChR loss and the presence of AChR‐Antibody complexes, other factors must determine the neuromuscular dysfunction in EAMG and possibly myasthenia gravis.