The archives of three bureaus of integrity are analyzed in order to study the reasons for reporting integrity and law violations within public organizations. Peer reporting accounts for only a small percentage of cases; most investigations originate from routine and continuous institutional controls. What are the reasons peers choose to report or not report? A sense of justice is most important, followed by self-protection and protection of the wrongdoer. The most important reason against coming forward is the reporter's fear of negative consequences. One surprising rationale for not reporting is that an individual feels responsible for the wrongdoer's punishment. Six propositions are elicited from this research as well as specific pragmatic recommendations for management procedures to improve reporting of integrity and/or law violations. Copyright © 2010 The American Society for Public Administration.