This chapter introduces students to theory and research at the interface of emotion and personality. The authors begin by defining emotion, noting that emotions have three key components. They are accompanied by distinct subjective feelings, bodily changes, and distinct action tendencies. The authors review several key issues in emotion research, beginning with the distinction between emotions as temporary states and emotions as enduring characteristics of a person. Next the authors discuss and differentiate the categorical and dimensional approaches to emotion. There is little consensus about the primary emotions among those working from the categorical approach, but the dimensional approach has identified two key dimensions—pleasantness/unpleasantness and arousal. The authors then distinguish emotional content and emotional style, noting that content refers to the “what” of emotional life, whereas style refers to the “how” of emotional life. The authors then review research on the content of emotional life, beginning with a review of research on pleasant emotions. In this section, the authors review empirical work on happiness and life satisfaction, including what we know about happy people, the relationship between money and happiness, and the relationship between personality and happiness. The authors present an empirically informed program to increase happiness. The authors then review theory and research on unpleasant emotions, beginning with anxiety, negative affectivity, and neuroticism. The authors review Eysenck’s biological theory and several cognitive theories of neuroticism. Next the authors address work on depression, and review diathesis-stress models of depression, and Beck’s cognitive theory of depression. The authors then review work on anger-proneness and hostility, highlighting research on the relationships between Type A personality and heart disease. The authors turn to a discussion of emotional style, highlighting theory and research on affect intensity. The authors close with a discussion of the interaction of emotional content (hedonic balance) and emotional style (affect intensity) as a way of understanding the distinct varieties of emotional lives.