Guillain-Barré syndrome (GBS), a neurologic disease that produces ascending paralysis, affects people all over the world. Acute infectious illnesses precede 50%-75% of the GBS cases. Although many infectious agents have been associated with GBS, the strongest documented association is with Campylobacter infection. The first line of evidence supporting Campylobacter infection as a trigger of GBS is anecdotal reports. The second line of evidence is serologic surveys, which have demonstrated that sera from GBS patients contain anti-Campylobacter jejuni antibodies, consistent with recent infection. Finally, culture studies have proven that a high proportion of GBS patients have C. jejuni in their stools at the time of onset of neurologic symptoms. Neurologic symptoms are more severe and more likely to be irreversible when GBS is preceded by C. jejuni infection. One of every 1058 Campylobacter infections results in GBS, and 1 of 158 Campylobacter type O:19 infections results in GBS.