A 29-year-old Haitian man had a sore throat with a marked tonsillar exudate followed by the onset of increasingly blurred vision with swallowing difficulties and, then, a diffuse acute demyelinating neuropathy. Cerebrospinal fluid showed moderate pleiocytosis and elevated protein content. Serological testing for diphtheria, but not for tetanus and poliomyelitis, was markedly positive. Other tests including HIV1 and 2, HTLV1 and Lyme disease were negative. Diphtheritic neuropathy should be considered in the differential diagnosis of Guillain-Barré syndrome in nonvaccinated patients.