We used the enzyme-linked immunosorbent assay to investigate autoantibodies against the gangliosides GM1, GD1a, GD1b, GT1b, GD2, and GQ1b in sera from 16 patients with Fisher's syndrome. We found high anti-GQ1b antibody titers, mainly those of the IgG class, in the sera of 13 of these patients. The titers decreased with the clinical course of the illness. Moreover, anti-GQ1b antibody-positive patients had more severe ataxia of cerebellar type than the antibody-negative patients.