I will argue that there are difficulties with the application of the four principles approach to incompetent children. The most important principle - respect for autonomy - is not directly applicable to incompetent children and the most appropriate modification of the principle for them is not clear. The principle of beneficence - that one should act in the child's interests - is complicated by difficulties in assessing what a child's interests are and to which standard of interests those choosing for children should be held. A further problem with the four principles approach is that parental authority does not follow clearly from the four principles.