In this chapter, we discuss three topics—privacy, security, and trust—which all have a variety of meanings in human contexts in a multidisciplinary view of the world. This presents a challenge in talking about any of them in isolation, and also in addressing questions of deciding what human–computer interaction (HCI) research might be relevant to each. To help set the context for this chapter, we will make use of a unifying scenario. As the discussion progresses, we will identify HCI research views that have been most useful in developing a productive research agenda for the field. The scenario below is drawn from our work in bridging the gap between business and technology perspectives in the area. As in our research work, we use the scenario to highlight issues rather than to offer an accurate picture of an existing situation or details of an idealized proposed solution.