This paper reviews the research literature on factors contributing to adolescent emotional well-being, focusing on generalized mood/affective states, emotion regulation and coping, and feelings about self, including self-esteem, self-efficacy, and locus of control. Each construct is defined and evidence from research is presented to indicate the importance of the construct as an element of well-being in adolescence. The empirical literature exploring antecedents and correlates of emotional well-being is then summarized. Finally, the paper discusses implications for policies, programs, and interventions designed to promote adolescent well-being. The focus is on research pertaining to each layer of the adolescent's ecosystem (individual, parent and family, peers, school, neighborhood, and community), emphasizing longitudinal studies that examine predictors of emotional well-being but use multivariate analyses to take background characteristics into account, and emphasizing experimental or quasi-experimental evaluation studies of programs to promote emotional well-being. Studies that have been replicated with similar results across different populations and geographic regions are highlighted. The paper restricts discussion to studies incorporating outcomes during adolescence and studies using non-clinical populations only. The paper concludes by noting that there is consistency in individual differences in adolescent emotional well-being. Individual differences are associated with characteristics of adolescents' environments, parent and family characteristics, school characteristics, and neighborhood and community characteristics. Several of the studies present implications for programs and school reform efforts. There was a strong association between emotional well-being and positive environments that provide adolescents with a sense of belonging, acceptance, and support for autonomy. Appended is a table of the review of research and implications for targeted activities to improve adolescent emotional well-being. (Contains 92 references.) (KB)