During 1990 to 1991, through a national surveillance program for poliomyelitis, the Paraguayan Ministry of Health received reports of 50 children with incident acute flaccid paralysis (< 15 years old). On the basis of established criteria, 37 were diagnosed with Guillain-Barré syndrome. The average annual incidence rate for 1990 to 1991 was 1.1/100,000 children. The clinical course was more benign than reported in other pediatric series. There were low rates of hospitalization (57%), respiratory compromise (8%), and intubation (5%). The overall severity, however, was similar to that described in previous reports, with a 3% case-fatality rate and an 81% total recovery rate at 12 months. Seventy-six percent of patients had symptom onset during January to April, the warmest months of the year. Thirty percent of patients had definite or possible exposure to organophosphate pesticides, and the peak use coincides with the peak incidence of Guillain-Barré syndrome. There was no correlation between occurrence of Guillain-Barré syndrome and prior immunization.