To clarify the clinical features of patients with anti-GM1b antibody, we retrospectively investigated which conditions were associated with anti-GM1b antibody in a large number of patients. Two hundred out of 1,713 patients had anti-GM1b antibody. One hundred and sixty-six (83%) were diagnosed with Guillain-Barré syndrome (GBS) or atypical GBS with preserved deep tendon reflexes. Our study suggests that the anti-GM1b antibody testing is useful for supporting the diagnosis of GBS. In addition, anti-GM1b antibody was detected in 18 patients with Fisher syndrome and the related conditions associated with anti-GQ1b IgG antibody, and 3 patients with ataxic GBS associated with anti-GD1b IgG antibody.