Having introduced the overall concept of deviant behaviors, the present chapter introduces the theoretical roots of interpersonal mistreatment and examines the relationships between earlier and more recent conceptualizations of this phenomenon. A wide range of definitions and constructs that demonstrate different aspects of interpersonal mistreatment is introduced, and reciprocities and differences between them are highlighted. This discussion eventually leads the reader to the central theme of the book-the concept of incivility.The roots of interpersonal mistreatment, as a concept, can be traced back to Gouldner's The Norm of Reciprocity (1960), and to another seminal study, now considered its counterpart, Reciprocity for Harm Done (Helm, Bonoma, & Tedeschi, 1972). Gouldner (1960), the first to address interpersonal reciprocation, defined a basic universal moral standard of reciprocity by suggesting that the norm of reciprocity was based on two interrelated demands: "(1) people should help those who have helped them, and (2) people should not harm those who have helped them" (p. 171). Twelve years later, Helm et al. (1972) introduced a negative norm of reciprocity, stating that people tend to negatively retaliate against those who had hurt them. One of the authors' interesting findings was that targets of aggressive interpersonal behaviours often perceived frequent aggressors as less attractive and less esteemed yet as more active and more potent, than infrequent aggressors. They further noted that participants in the study tended to inflict more harm than they had received when the frequency of the original harmful actions against themselves was low, yet when this frequency was high, they tended to retaliate with less intensity. These findings suggest that the frequency of deviant interpersonal behaviors impacts targets' reactions. Indeed, throughout this chapter, we will discuss the role of frequency as part of the definitions of interpersonal mistreatment and targets' reactions to it. We will begin by introducing Nora's (not her real name) account.It all started in October 2005, when I was appointed finance and procurement manager by the head of my department. Following the appointment, Rachel [not her real name], my direct superior, summoned the department secretary and myself to a meeting. She said that my new duties did not add up to a full-time position and therefore, she decided to assign some of the secretarial duties to me. I pointed out that I had been promoted to my new position (finance