ADs began as simple requests to avoid medial treatment that would prolong life in undesirable conditions. However, they have evolved, becoming increasingly detailed and specific, often containing patient preferences for a variety of medical treatments in hypothetical medical scenarios. The activities leading up to the completion of an AD -- discussion of clinical circumstances and prognosis, understanding a patient’s goals in this clinical context, and outlining plans for future care to approximate those goals -- constitute the process of advance care planning (ACP), which is central to end-of-life decision making and AD completion. ACP, in its most advanced form, is a comprehensive, ongoing, and holistic communication pattern between a physician and his or her patient (or the patient’s designated proxy) about values, treatment preferences, and goals of care. ACP broadens the framework of ADs by emphasizing not only decisions about whether to use a treatment but also by making practical arrangements (e.g., anticipating treatment modalities to have them in place). Additionally, ACP helps to identify what course serves the patient best and then outlines specific steps to make that course more likely. Thus, ADs are not an end in themselves; rather, these documents are most effective when incorporated into a comprehensive ACP process and the patient’s goals are incorporated into the care provided by the health care system to the patient. This report examines the empirical evidence about the degree to which ADs and ACP have met their intended goals. We explore what the medical literature reports concerning the use of ADs and ACP, disparities among groups in their use, and interventions to enhance the use and value of ADs and ACP.