Antiganglioside antibodies are known to play a pathogenic role in development of Guillain-Barré syndrome (GBS) and Fisher syndrome (FS). Recently, antibodies to ganglioside complexes (GSCs) consisting of two different gangliosides were found in some patients with GBS and FS. Some anti-GSC antibodies such as anti-GD1a/GD1b, anti-GM1/GQ1b or anti-GM1/GalNAc-GD1a antibodies correlate with specific clinical features. Anti-GSCs antibodies can be found also in chronic inflammatory demyelinating polyneuropathy and neuropathy associated with IgM monoclonal gammopathy. Latest studies have revealed molecular basis of anti-GSCs antibody-mediated nerve injury. The concept of GSCs will provide new vistas on understanding of pathogenesis of GBS and related autoimmune diseases.