Health care data are collected and managed by multiple organizations, often residing in information systems that are disconnected from the rest of the health system. Interoperability and health information exchange (HIE) are concepts that describe methods for data to be shared among these data siloes. Public health organizations are both senders and receivers of data, and there exist multiple efforts to facilitate HIE and interoperability in health systems around the world. This chapter explores HIE and interoperability in the context of public health. The chapter describes how HIE efforts are enabling health care providers to report infectious as well as chronic disease data to public health agencies. Furthermore, the chapter examines activities such as syndromic surveillance and public health registries from an interoperability perspective. The chapter also examines the drivers and barriers to HIE from a public health context, and it explore trends likely to influence interoperability in the future.