The introduction in Britain of advance directives--which allow a person to state in advance of becoming incompetent that they wish to take part in treatment decisions when no longer mentally competent--has now been advocated by the medical and legal establishments. The practical application of directives relating to health care would be simplified by the adoption of a standard model document together with guidelines summarising the background clinical conditions and any subsequent acute events that may make it appropriate to trigger the use of a directive. As no specific legislation exists, good communication is needed at the various stages between the drafting and implementation of directives if the system of directives is to be successful.