The widespread adoption of personal service robots will likely depend on how well they interact with users. This chapter was motivated by a desire to facilitate the design of usable personal service robots. Toward that end, this chapter reviews the literature concerning people interacting with personal service robots. First, ongoing research related to the design of personal service robots is discussed. This material is organized around generic activities that would take place when a user initiates interaction with a future personal service robot, for example, understanding the robot's affordances or its cognitive capabilities, as well as when a personal service robot initiates interaction with a user, for example, understanding the user's intent or engaging and communicating with the user. Second, research areas that deserve more attention from the human-robot interaction community are discussed, for example, understanding when people do and do not treat robots as if they were people. Throughout the chapter, recommendations for the design of future personal service robots are offered along with recommendations for future research. S imple robots that perform a household chore or entertain are becoming commonplace, and more sophisticated versions of those robots are just on the horizon. Such sophistication, however, could translate into difficulty interacting with those robots. To avoid that difficulty, designers must be concerned about human-robot interaction. Toward that end, this chapter reviews the literature concerning how robots that perform chores or entertain should interact with people. THE DIvERSIfIcATIon of commERcIAl RoboTS The United Nations categorizes commercial robots as industrial robots, professional service robots, or personal service robots (United Nations, 2008). An industrial robot is an "automatically controlled, reprogrammable, multipurpose manipulator programmable in three or more axes" (International Organization for Standardization, 1994). For example, the first industrial robot, known as the Unimate, was a large programmable arm that handled and stacked hot pieces of die-cast metal at a General Motors plant. Unlike industrial robots, professional service robots and personal service robots do not have standardized definitions. For the most part, they are differentiated from one another on the basis