In 1975, clinical, electrodiagnostic, and pathologic features defined chronic inflammatory demyelinating polyneuropathy (CIDP). Subsequent reports have made it clear that demyelination is a cardinal feature of teh disorder. Over the past 30 years, variants have been described and associated systemic disorders identified. There continues to be discussion, however, as to how best to define CIDP and classify the disorders that are chronic, acquired, immune mediated, and demyelinating. Understanding the disorders allows clinicians to make appropriate treatment decisions. Some disorders originally considered as variants now are shown to have characteristic features that make them distinct from CIDP. It is imperative to recognize the differences between these disorders.