This chapter will largely view HCI in its broader context. HCI is not just about user interfaces but also about the user experience  of systems: how people perceive and understand, reason and learn about, and react and adapt to digital technologies. To borrow the terminology Sasse and Flechais2  use in discussing security, HCI has come to deal not only with process  (how systems are used, designed, and developed) and product  (the systems themselves and their interfaces), but also panorama  (cultural and organizational contexts that support, discourage, or otherwise shape the systems they envelope). Privacy, like security, implicates all of these levels. It is by its nature both a question of the user and his or her data but also the user and others’ use of that data. Our interests, therefore, will be those of HCI-writ-large.While HCI has gone through several generations of computational technologies, it has carried a number of research themes forward. As mentioned, this chapter will consider the various HCI themes and their research findings that may be important when designing, constructing, or evaluating privacy mechanisms. Before exploring these HCI research streams, however, we first need a working definition of privacy, and to compare and contrast privacy concerns with HCI concerns.