This chapter examines research on the enactment and perception of deception. Specifically, interpersonal deception theory argues that a liar's communication consists of both intentional (strategic) attempts to appear honest and unintentional (nonstrategic) behaviors that are beyond the liar's control. The chapter suggests that many scholars have expressed skepticism about certain assumptions contained in interpersonal deception theory and the four-factor model. It discusses the ways in which characteristics of the liar-in addition to characteristics of the lie being told and the deceptive situation-affect the process of deception. The chapter examines the opposite side of the coin: deception detection. It also suggests that one possible way to improve deception detection is by training people to spot reliable cues to deception. The fact that people are not very accurate at detecting deception is unfortunate when you consider the practical and professional contexts within which accurate detection would be desirable for jurists, consumers, law officers, negotiators, customs inspectors, job interviewers, secret service agents.