Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is one of several chronic acquired demyelinating neuropathies that are considered to be autoimmune diseases. The prevalence of these illnesses may be underestimated because of limitations in clinical, serologic, and electrophysiologic diagnostic criteria. An Ad Hoc Subcommittee of the American Academy of Neurology (AAN) proposed a set of diagnostic criteria for CIDP to be used for research purposes, and several other criteria followed. Of these, the AAN electrophysiologic criteria are the most restrictive and fit only a subset of patients with CIDP. Other criteria, including the Inflammatory Neuropathy Cause and Treatment (INCAT) clinical and electrophysiologic criteria and the Nicolas or Thaisetthawatkul electrophysiologic criteria, are more sensitive and can therefore identify a broader range of patients with CIDP for clinical trials. Regardless of which criteria are chosen for use in clinical trials, patients who fall outside of these criteria may also have CIDP and may benefit from treatment. Unfortunately, because of the lack of clarity with regard to diagnostic criteria for CIDP, many patients remain untreated. In addition, certain CIDP variants may also respond to treatment. These include sensory CIDP, multifocal motor neuropathy (MMN) with or without conduction block, multifocal acquired demyelinating sensory and motor (MADSAM) neuropathy, distal acquired demyelinating sensory (DADS) neuropathy, and multifocal acquired sensory and motor (MASAM) neuropathy. Therefore, although patients may not meet the diagnostic criteria for inclusion in clinical trials of CIDP, they may still benefit from current and future treatments used in CIDP.