A Practice Note explaining the key issues to consider when asserting and litigating the attorney-client privilege and the work product doctrine in Illinois circuit court civil litigation, including when the attorney-client privilege and work product doctrine apply, who can assert the privileges, and how to assert the privileges in response to testimony, deposition notices, document requests, interrogatories, requests for admissions, and subpoenas. This Note also examines privilege logs, inadvertent disclosures, challenges to a privilege assertion, the sources of law for the attorney-client privilege and work product doctrine, and appellate review of privilege rulings.