SUMMARYThe mechanism of absent or decreased deep tendon reflex in Eaton‐Lambert syndrome was studied. There was no evidence suggestive of the presence of a neuropathy. On the other hand, a brief (about 10 seconds) maximal voluntary contraction made the absent deep tendon reflexes elicitable, which suggests that the block of neuromuscular transmission in Eaton‐Lambert syndrome is responsible for the absent or decreased deep tendon reflex. Such enhancement of the decreased deep tendon reflex in Eaton‐Lambert syndrome might be helpful in differentiating neuropathy and Eaton‐Lambert s