Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired, immune-mediated peripheral neuropathy. In recent years, the application of basic principles of general immunology has widened our understanding of the etiology and immunopathogenesis of this neuropathy. Although both cellular and humoral factors have been implicated, the data are still fragmentary and insufficient for a unified hypothesis. This review summarizes the present knowledge of the fundamental immune mechanisms related to the immunopathogenesis of CIDP and discusses the role of T cells, activated macrophages, cytokines, co-stimulatory molecules, and anti-myelin antibodies. An important factor in current approaches to the therapy of CIDP is the increasingly recognized concomitant axonal loss that occurs secondary to primary demyelination.