 Under what conditions, if any, is it permissible to impose such a risk on someone who will receive no therapeutic benefit? For competent people, it is overwhelmingly accepted that their valid consent is a necessary condition of morally permissible retrieval. (A very few writers disagree, e.g., Rakowski 1991 and, less clearly, Fabre 2006). But even if consent is necessary, it may not be sufficient, and a further question is how much risk it is permissible to impose even on those who consent. Living donor transplantation also raises important questions about the validity of consent and about whether organs may ever be taken from healthy non-competent people, such as children.