The Guillain-Barré syndrome (GBS) is an acute immune mediated polyneuropathy. Diagnosis of clinically defined GBS is based upon symmetrical weakness developing within 4, but usually within 2 weeks and disappearance of myotatic reflexes. There is a large variability in clinical expression, including bulbar variants. Also laboratory characteristics may vary. Therefore, at present, diagnosis is based on the clinical parameters. In the individual patient characteristics of EMG, immunological and microbiological studies and sometimes pathological and epidemiological information may further define a more specific pattern. At present it seems not worthwhile to split up GBS in subgroups, although in the future subpatterns responding to specific therapy may be defined. The pathogenetic studies point at present to molecular mimicry as a possible mechanism in triggering off the disease. In the cranial nerve variant with ophthalmoplegia and ataxia antibodies against the ganglioside GQ1b are found that recognize similar epitopes on specific Campylobacter jejuni strains; for the classical ascending form similar observations are made between anti-GM1 antibodies and C. jejuni. Treatment is in the first place supportive. Plasma exchange has been the first proven effective specific treatment. High dose immunoglobulins (IgIV) are at least as effective and in fact was somewhat, but significantly superior with respect to some outcome criteria in the first large scale clinical trial. Several studies using different treatment schedules are at present underway. In the Netherlands a pilot study with the combination of IgIV and high dose methylprednisolone gave very promising results compared to IgIV alone. This was in contrast with an international study evaluating methylprednisolone, either alone or in combination with plasma exchange. The combination of IgIV with methylprednisolone is now further investigated in a formal randomized, double blind trial aimed to include 225 patients.