Human population genetics has entered a new era of public interest, of controversy, and of ethical problems. Population genetics raises novel ethical problems because both the individuals and the populations being studied are, in effect, "subjects" of the research. Those populations are collectively subject to possible benefits and harms from the research and have interests, somewhat different from those of the individuals, that must be considered from both ethical and practical standpoints. The chapter first describes the new setting for research in human population genetics. It then examines the most controversial ethical issue in population genetics-whether researchers must obtain the informed consent of both the individual subjects and the group as a collectivity. Other vexing issues, including special problems caused by researchers' commercial interests, confidentiality, control over research uses and materials, and return of information to the population are also considered.