It has been argued elsewhere that "consent is the hallmark of our health care system". If this is correct, then what is the position of those who are not capable of deciding whether (or not) to give consent to health care? This paper briefly examines the law and ethics of substitute decision-making. Its principal arguments are three. Firstly, that because exercising a choice (or exercising one's autonomy) presupposes the capacity to do so, there are an increasing number of people who are not capable of exercising their autonomy in health care settings. Second, that as they are not capable of making an autonomous choice, the law permits another fundamental bioethical principle, that of beneficence, to operate so as to ensure that such people are not denied treatment which they may need. This principle is reflected in the use of Guardianship tribunals. Finally, very brief comment is made on the leading difficulty in this field, which is ascribing a clear meaning to the term competency--the standard which separates the people who are permitted to exercise an autonomous choice, and those not permitted to do so.