This article addresses the ethical and legal duties that must be confronted in any study of the risk of interpersonal violence in the community. Ongoing research--the MacArthur Risk Assessment Study--on the markers of violence among released mental patients is taken as illustrative. Methods by which the researchers are discharging their legal and ethical duties are described and justified. Strategies center around the duty to protect research subjects from their own violence, and the duties to protect research staff and third parties from subjects' violence. By airing these rarely discussed issues, the authors hope to initiate a professional dialogue on crucial ethical and legal aspects of the research process.