This RAND working paper documents the proceedings of a daylong workshop, “Ethical Principles in Social-Behavioral Research on Terrorism: Probing the Parameters.” The workshop was convened to initiate a public discussion of the parameters that should guide the ethical conduct of social and behavioral research on terrorism that is frequently carried out in countries or among groups hostile to the United States. The workshop was organised into three sessions on the topics of “Deception and Concealment vs. Autonomy,” “Maximizing Beneficence and Maintaining Justice,” and “Ensuring Confidentiality.” Each session included a main speaker followed by short presentations from an expert panel, a plenary discussion, and a wrap-up by the session chair. All proceedings were taped and transcribed. The transcriptions of the presentations by the speakers and panelists have been lightly edited to improve readability, as have the introductory and wrap-up comments by the workshop organisers. The transcriptions of the plenary discussions have been summarized to highlight the main points.