In a landmark decision, the U.S. Supreme Court affirmed a Missouri ruling that sharply limited family decisions about life-sustaining treatment for incompetent patients. The Court held that the Constitution protects the refusal of life-sustaining treatment by competent patients. For incompetent patients, states may require "clear and convincing" evidence of refusal, specifically for the withdrawal of tube feedings, if such a person were in a persistent vegetative state. The ruling left many clinical questions unanswered, such as whether life-sustaining treatment must be given to terminally ill incompetent patients, whether patients may refuse artificial feedings, and what constitutes clear and convincing evidence of refusal. The decision also has potentially harmful consequences. It may undermine family decision making, encourage cynicism and disregard of the law, and promote defensive medicine. Physicians can minimize such consequences by encouraging patients to provide advance directives, such as the durable power of attorney for health care, by urging legislative action, and by setting national practice standards for decisions regarding incompetent patients.