Confidentiality is a core value in medicine and public health yet, like other core values, it is not absolute. Medical ethics has typically allowed for breaches of confidentiality when there is a credible threat of significant harm to an identifiable third party. Medical ethics has been less explicit in spelling out criteria for allowing breaches of confidentiality to protect populations, instead tending to defer these decisions to the law. But recently, issues in military detention settings have raised the profile of (...) decisions to breach medical confidentiality in efforts to protect the broader population. National and international ethics documents say little about the confidentiality of detainee medical records. But initial decisions to use detainee medical records to help craft coercive interrogations led to widespread condemnation, and might have contributed to detainee health problems, such as a large number of suicide attempts several of which have been successful. More recent military guidance seems to reflect lessons learned from these problems and does more to protect detainee records. For the public health system, this experience is a reminder of the importance of confidentiality in creating trustworthy, and effective, means to protect the public's health. (shrink)