Guillain-Barre syndrome (GBS) is a reactive, self-limited, monophasic disease triggered by a preceding bacterial or viral infection. GBS has also been linked to underlying systemic diseases, certain malignancies, surgery, pregnancy, trauma severe infection, and tissue transplantation (bone marrow and organs). Although its pathogenesis is unclear, it is likely to be a consequence of an immune mediated process. Therefore, we believe that GBS results from an aberrant immune response that somehow mistakenly attacks the nerve tissue of its host, most probably by recognizing a molecular similar epitope mechanism (molecular mimicry). Immune reactions against these epitopes result in acute inflammatory demyelinating neuropathy or acute axonal forms. GBS has a worldwide distribution with an annual incidence of approximately 1.2-8.6 cases per 100,000 people. Both genders are at similar risk (but there is a slight male predominance). All ages are affected, although the distribution is bimodal. The supporting measures are critically important to provide optimal treatment. Immunomodulation with plasma exchange and intravenous immunoglobulin treatments shorten the disease course. Outcome is generally good, with virtually full recovery in 70-80% of the patients. In this review physiopathological aspects and clinical implications of GBS are fully discussed.