When patients approach the end of life, their loved ones often do not know how much treatment is too much and struggle to decide when to stop intervening and allow them to die in peace. Conversely, health care professionals may tend to prescribe extraordinary means of life support, sometimes simply because of legal and fiscal concerns or a family’s request for futile care. It can be useful to refer to the general bioethical principle that, typically, there is no moral obligation to provide a substitute for vital organs. In this context, providing a substitute for a vital organ means wholly replacing the vital function of the dying organ by means of either a transplant or medical machinery. This article seeks to explain how this rule may be applied when a patient and his family are deciding at what point to stop treatment and allow the patient to die in peace.