Advance directives have been promoted as being the best device for making decisions on behalf of patients who are unable to speak for themselves. It is believed that an advance directive would tell the health care professionals what to do. Conflicts would dissolve and the course would become clear. Such hopes and expectations probably exceed the capacity of these documents to provide context-based, real-time decisions. This article reviews the research on advance directives, including proxy and instructional documents, and discusses the strengths and limitations of each. Advance directives are often thought of as static, binding documents. Recommendations will be offered on how to use these documents as tools to facilitate patient-centered, dynamic decisions.