A document directing, in advance, what medical actions should be taken if the person receiving the care is unable to make those decisions. Living Wills and DNR (Do Not Resuscitate) orders are types of advance directives, but such directives can also specify that you do want a particular type of care no matter what happens, and they are not limited to terminal illnesses.

Advance directives are generally pretty simple legal documents, but exactly what has to be stated in them varies from location to location (an advance directive valid in one U.S. state may not be valid in another). Generally, though, if someone's wishes are stated in written form, that gives those wishes more weight in court. Doctors and other medical personnel are usually allowed to refuse to carry out someone's wishes on the grounds of their own conscience, but they often will refer the patient to someone who will carry their wishes out.

Without an advance directive, the family of the patient will be asked to make the decisions if they are available. They may not know what the incapacitated person would want; they may disagree between themselves; or they may not agree with what they have been told the incapacitated person would want. An advance directive allows you to appoint a particular person as your agent who you trust to carry out your wishes. (In some places this is called a Health Power of Attorney.) The advance directive can state exactly what you want in addition to appointing an agent. You can also name alternate agents in case the first agent can't or won't serve in the position, and you can revoke a person's appointment as your agent at any time. You can also suggest a guardian for the court to appoint if you become permanently incapacitated.

If you make an advance directive, several family members and the doctors you normally see should have a copy -- it can't be acted on if no one knows what it says.