The virologic, clinical, epidemiologic, and immunologic aspects of an epidemic of acute polyradiculoneuropathy that occurred in Itagui, Colombia, in May 1968, are presented. Clinically, the cases fit the classic description of the Guillain-Barré syndrome. Epidemiologically, an unusually high number of consultations for respiratory and gastrointestinal disease was noted in the town during the month prior to the epidemic. Sera from 6 of 14 patients studied contained complement fixing antibodies against human brain. This outbreak is compared with previous reports of epidemic polyneuritis.