End-of-life care of critically ill patients generally consists of two closely related practices: the withholding and withdrawal of life support, and the administration of palliative care. In the United States, the withholding or withdrawal of life support is legally justified by the principles of informed consent and informed refusal. The U.S. Supreme Court has held that competent patients may refuse any and all treatments, including those that sustain life. All states sanction such refusal by competent patients, and most states allow surrogates to refuse treatment on behalf of incompetent patients. Although some physicians use the concept of futility to unilaterally withhold or withdraw life support, the Supreme Court has not heard a futility case, and the only clear legal rule on futile treatment is the traditional malpractice test, which measures physician actions against standards of medical care. However, the Supreme Court has furnished guidelines on the administration of palliative care. By using the principle of double effect, these guidelines allow physicians to give sedative and analgesic agents to dying patients if they intend to relieve pain and suffering but not to hasten death.