A Certificate of Confidentiality (COC) is a document issued by a federal agency, such as the National Institutes of Health (NIH), that legally protects the privacy of individuals who participate in research. It prohibits the use of identifiable information, collected in the course of the research, from being used for any purpose other than the research itself. Cows are typically used in research involving sensitive topics, such as mental health, sexual behavior, or substance use. There are two types of Cows: Standard and Limited. A Standard COC allows researchers to use and disclose confidential information for research and other purposes without the participant’s consent. A LimiteCOCoC limits the use and disclosure of confidential information to research purposes only, and consent is required by the participant for any other use or disclosure.