Although many people have written about the Guillain-Barré1 syndrome, few have stated clearly their criteria for diagnosis.2-9 Confusion has been created by those who would make the diagnosis in cases of infections with recognized neuritic sequelae (as diphtheria), diseases which can cause elevation of the cerebrospinal fluid (CSF) protein without pleocytosis (as diabetes), and neuritides that are well-known following certain inoculations. In the present state of knowledge, it would seem best to consider as Guillain-Barré syndrome only those conditions in which the cause of the polyradiculoneuropathy is unknown. This is a report of 100 patients observed at the University of Michigan Hospital between 1940 and 1963, meeting these criteria (modified from DeJong10): (1) The paralytic illness may follow a nonspecific infection, but there is no preceding or accompanying illness of a type known or thought to be associated with polyradiculoneuropathy; (2) Sensory involvement may occur but