The concepts of Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP) have changed over the last decade. The spectrum of GBS ranges from acute inflammatory demyelinating polyneuropathy to pure motor, sensory-motor or bulbar variants and the Miller Fisher syndrome. Also CIDP includes different variants in addition to the typical clinical picture with symmetrical proximal and distal weakness, such as a form with predominant distal weakness, a pure sensory form, an asymmetric form and a form with predominant cranial nerve involvement. Detailed immunopathologic features have been described in GBS and CIDP: most current investigations are centered on the hypothesis of molecular mimicry in GBS and together with the pathogenic role of cell-mediated immunity different antibodies have been discovered in GBS which interfere with nerve impulse conduction on neuromuscular transmission. The immunopathogenesis of CIDP remains fragmentary and insufficient for a unified hypothesis. Activated macrophages and T-cells with the participation of T-1 helper cell related cytokines seem to play a fundamental role in demyelination. The nature of antigen presenting cells, T-cell receptors, adhesion molecules and the proinflammatory cytokines need to be explored to design more specific immunotherapies. Established treatments in GBS include intravenous immunoglobulin and plasma exchange. Randomized trials have shown the efficacy of prednisone, intravenous immunoglobulin and plasma exchange in CIDP. New insight in the pathogenetic role of the cytokine-network in CIDP opens new therapeutical possibilities with the modification of the T-1 helper cell reaction with interferon.