Considerable theory and research on self-esteem reveals that high self-esteem confers many benefits to individuals and that it relates to many positive psychological outcomes. Increasingly, however, it has become clear that high self-esteem also has a dark side, as it sometimes relates to maladaptive outcomes such as heightened aggressive behavior. Therefore, it is extremely important to determine when high self-esteem relates to positive psychological functioning and outcomes and when it does not. One critical factor may be the extent to which high self-esteem is fragile or secure. Individuals with fragile high self-esteem appear willing to go to great lengths to preserve, maintain, and enhance their positive feelings of self-worth. Defensiveness and other maladaptive processes appear to characterize these individuals. In contrast, individuals with secure high self-esteem have well-anchored feelings of self-worth that relate to healthy psychological functioning and positive outcomes. Past research on stability of self-esteem indicates that one way to distinguish between fragile and secure high self-esteem is to determine the extent to which individuals' self-esteem is stable over time; the more unstable self-esteem is, the more fragile it is. The proposed research will promote understanding of self-esteem processes by focusing on multiple representations of this fragile-secure distinction. Specifically, research is proposed to examine (a) discrepancies between individuals' implicit (i.e., automatic, highly efficient, and largely nonconscious) and explicit (i.e., deliberate and conscious) self-esteem; (b) contingent self-esteem, (i.e., the extent to which feelings of self-worth are dependent upon the achievement of specific outcomes or evaluations); (c) stability of self-esteem (i.e., the magnitude of short-term fluctuations that people experience in their contextually-based feelings of self-worth); (d) narcissism; and (e) defensiveness. Though different in their particulars, each of these constructs reflects a component of self-esteem that is distinct from its level (i.e., general or typical feelings of self-worth). Six proposed studies examine individual differences in these markers of fragile versus secure self-esteem, in the context of their implications for pressing societal problems, namely aggression and prejudice, as well as for everyday social conflicts, verbal defensiveness, and close relationship functioning, quality and satisfaction. Study 1 focuses on defensive verbalizations in response to self-threat. Study 2 focuses on aggression following interpersonal rejection. Study 3 focuses on prejudice, Study 4 focuses on the occurrence of conflict within everyday interactions, and Studies 5-6 focuses on reactions to threats and close relationship functioning. A common thread in each of these studies is to examine the role of verbal defensiveness, which is a relatively direct index of people's tendencies to process threatening experiences defensively (Feldman Barrett et al., 2002). Taken as a whole, these studies allow for a comprehensive examination of the processes associated with fragile versus secure high self-esteem in a range of interpersonal contexts. The long-range objectives are to understand better the nature of high self-esteem and its role in psychological functioning and interpersonal relations.