Answering important public health questions often requires collection of sensitive information about individuals. For example, our understanding of how HIV is transmitted and how to prevent it only came about with people's willingness to share information about their sexual and drug-using behaviors. Given the scientific need for sensitive, personal information, researchers have a corresponding ethical and legal obligation to maintain the confidentiality of data they collect and typically promise in consent forms to restrict access to it and not to publish (...) identifying data.The interests of others, however, can threaten researchers' promises of confidentiality when legal demands are made to access research data. In some cases, the subject of the litigation is tightly connected to the research questions, and litigants' interest in the data is not surprising. Researchers conducting studies on tobacco or occupational or other chemical exposures, for example, are relatively frequent targets of subpoenas. (shrink)