• Rapid eye movements, having high velocity and low amplitude, are described in 11 patients with myasthenia gravis. These movements occur with various degrees of ophthalmoplegia. To distinguish them from the somewhat similar lidtwitch phenomenon, they are called quiver movements. We believe that their presence is pathognomonic of myasthenia and results from a differential involvement of the two myoneural mechanisms that are peculiar to the extraocular muscles.