The clinical and electrophysiologic findings in 10 patients with Miller Fisher syndrome (ataxia, ophthalmoplegia, and areflexia) were reviewed. All patients had motor and sensory nerve conduction studies and EMG in the arm and the leg, and seven patients had cranial nerve conduction studies. Electrodiagnostic abnormalities were found in all patients and were characteristic of an axonal neuropathy or a neuronopathy with predominant sensory nerve changes in the limbs and motor damage in the cranial nerves. The pattern of abnormalities was distinct from the usual features seen in the major form of acute inflammatory polyneuropathy, the Guillain-Barré syndrome.