The United States, along with other nations and international organizations, has developed an elaborate system of ethical norms and legal rules to govern biomedical research using human subjects. These policies govern research that might provide direct health benefits to participants and research in which there is no prospect for participant health benefits. There has been little discussion, however, about how well these rules would apply to research designed to improve participants’ capabilities or characteristics beyond the goal of good health. When mentioned at all in the literature, this so-called enhancement research, as opposed to research aimed at diagnosing, preventing, curing, or treating illnesses or medical conditions, is usually dismissed without explanation.