The utility of including personality in a battery of predictor measures continues to be debated, even though there is an extensive literature and thousands of empirical studies (Barrick & Mount, 2005; Morgeson, Campion, Dipboye, Hollenbeck, Murphy, & Schmitt, 2007; Ones, Dilchert, Viswesvaran, & Judge, 2007). This chapter comprehensively reviews what we know and do not know about personality in personnel selection research and practice. We begin with a brief review of the history of psychological testing and personnel selection. Next, we review the relationships found between personality traits, primarily those from the Big-Five Model, to other individual differences. This is followed by a summary of evidence for the predictive validity of personality at work and in life more broadly, which than shifts to a discussion about emerging conceptual or theoretical directions, focusing on when (moderators) and how (mediators) personality affects work attitudes, behaviors, and outcomes. We conclude the chapter by discussing critical measurement issues, particularly response distortion, and legal implications.