IgG anti-ganglioside antibodies are present in a proportion of patients with the Guillain-Barré syndrome (GBS). To determine if antibodies to gangliosides are restricted in IgG subclass distribution, we evaluated IgG subclass antibody responses to gangliosides in sera of patients with GBS. Sera from GBS patients with IgG activity against gangliosides were analyzed for IgG subclass distribution using an enzyme-linked immunosorbent assay. The anti-LM1 antibodies in sera from GBS patients were predominantly of the IgG3 subclass while anti-GM1 and anti-GT1a antibodies were predominantly of the IgG1 and IgG3 subclasses. The results indicate a Th2-dependent antibody response.