Of 23 neuromyelitis optica (NMO) cases, we found two cases with oligoclonal IgG bands (OBs). Both patients were positive for NMO-IgG. Their common features were long disease duration and co-existing autoimmune diseases (myasthenia gravis and sicca syndrome). Although OBs are mostly negative in NMO, which distinguishes it from multiple sclerosis (MS), they can be positive by long-standing autoimmunity, which may not be directly related to NMO.