For most of political science's history, discussions about professional ethics had nothing to do with human subjects. Professional ethics involved integrity in the classroom, fair tenure and promotion rule, and the careful avoidance of plagiarism. As most research was observational, there was little need for attention to how scholarly activities might directly affect the subjects of our work. Times have changed. The dramatic growth in the use of experiments in social science, especially overseas, is generating unexpected ethical controversies. The purpose of this volume is to identify, debate, and propose practical solutions to the most critical of these new ethical issues.