For many years the prevailing paradigm for medical decision making for children has been the best interest standard. Recently, some authors have proposed that Mill’s “harm principle” should be used to mediate or to replace the best interest standard. This article critically examines the harm principle movement and identifies serious defects within the project of using Mill’s harm principle for medical decision making for children. While the harm principle proponents successfully highlight some difficulties in present-day use of the best interest standard, the use of the harm principle suffers substantial normative and conceptual problems. A medical decision-making framework for children is suggested, grounded in the four principles. It draws on the best interest standard, incorporates concepts of harm, and provides two questions that can act as guide and limit in medical decision making for children.