The association between Campylobacter jejuni infection and Guillain-Barré Syndrome (GBS) was investigated serologically in 52 GBS patients. The specific antibody titers of immunoglobulin G class to C. jejuni were measured in the patient' sera using an enzyme-linked immunosorbent assay with acid-extracted antigen. The analysis showed that 31 (59.6%) of the 52 patients had evidences of recent C. jejuni infections in contrast to 16 (8.9%) of 180 healthy persons. The seropositive patients were analyzed with respect to the nature of their anticedent events. C. jejuni antibodies were found in 22 (75.9%) of the 29 patients with diarrhea, one patient with esophagus cancer, 4 (30.8%) of the 13 patients with upper respiratory infections, and 4 (50.0%) of the 8 patients without any symptoms, respectively. These findings support that there may be a close relationship between C. jejuni infection and the GBS with preceding diarrhea.