Treatment for Miller Fisher syndrome (MFS) is controversial, and even the natural history and prognosis are not fully understood. We retrospectively reviewed our cases of MFS for the last 3 years. The analysis of 4 MFS cases revealed that we had performed plasmapheresis or additional immunotherapy to each of 4 patients, and their symptoms resolved for up to 50 days after the onset (ataxia improved 20-35 days and ophthalmoplegia for 25-50 days) except for 1 patient, and that Guillain-Barré syndrome had been diagnosed in 1 patient who had developed profound muscle weakness. We also discovered that MFS patients had a deviated T-helper Type-1 (Th1)/T-helper Type-2 (Th2) polarization and that plasmapheresis can shift Th2-dominant status to Th1-dominant status in patients with MFS. Although plasmapheresis may remove humoral factors, including anti-GQ1b, and may induce a shift of the Th1/Th2 cytokine-producing cell balance in peripheral blood, the therapeutic rationale has not yet been established. Therefore, controlled clinical trials are required to show whether plasmapheresis leads to earlier recovery with fewer neurologic deficits in patients with MFS.