This chapter describes self-esteem and provides an overview of existing perspectives on self-esteem. Self-esteem is a sociometer, essentially an internal monitor of the degree to which one is valued or devalued as a relational partner. The chapter evaluates a series of specific, testable hypotheses about self-esteem and examines laboratory and other findings in relevance to the sociometer theory and its specific hypotheses. This sociometer theory also reinterprets several interpersonal phenomena that have been explained previously in terms of the self-esteem motive. In specific, self-esteem refers to a person's appraisal of his or her value. Global self-esteem denotes a global value judgment about the self, whereas domain-specific self-esteem involves appraisals of one's value in a particular area. Self-esteem is an affectively laden self-evaluation. Self-evaluations are in turn assessments of one's behavior or attributes along evaluative dimensions. Some self-evaluations are dispassionate. whereas others are affectively laden. Self-esteem focuses primarily on individual differences in dispositional or trait self-esteem.