This study will measure how adults with CIDP receiving IVIg treatment adjust to efgartigimod PH20 SC. The study duration for each participant will be approximately 17 to 19 weeks.

Inclusion Criteria:

• Is at least 18 years of age and the local legal age of consent
• Is diagnosed with CIDP (confirmed or possible CIDP) according to the criteria of the European Academy of Neurology/Peripheral Nerve Society
• Is being treated with IVIg every 3-6 weeks, on a stable dose and dosing interval (between 0.5-2 g/kg) for at least 3 doses
• If receiving oral corticosteroids, this should be at a stable dose of less than 20 mg a day or less than 40 mg every other day, for at least a month.
• If receiving nonsteroidal immunosuppressive medication, this should be at a stable dose for at least 3 months

Exclusion Criteria:

• Besides the indication under study, known autoimmune disease or any medical condition that would interfere with an accurate assessment of clinical symptoms of CIDP or puts the participant at undue risk
• Types of other polyneuropathy other than CIDP