Isolated bilateral internal ophthalmoplegia is a rare and problematic condition affecting activities of daily living. Herein, we describe the cases of 2 patients with postinfectious isolated bilateral internal ophthalmoplegia, i.e., mydriasis without external ophthalmoplegia. One patient demonstrated no other neurological symptom, while the other patient showed mild gait ataxia. Magnetic resonance imaging revealed no abnormal findings in the brain or brainstem. Light-near dissociation of the pupils was not recognized in either patient, and supersensitivity to dilute pilocarpine was observed in 1 of the 2 patients. An increased titer of the anti-GQ1b IgG antibody was noted in 1 patient. A review of the literature revealed five similar cases; the symptomatic characteristics, ratio of positive anti-GQ1b IgG antibody, and effective treatment are discussed.