ABSTRACT. Background and aims: The present study investigated stability and change in emotional well-being in a prospective study of a large sample of community-dwelling older adults (> or = 55 years). Emotional functioning was conceptualized according to the tripartite model distinguishing three aspects: general negative affect (NA), depression, and anxiety. The study tested models for the decline of mental health in late life based on the diathesis-stress model. In previous studies, support has been found for the diathesis-stress model (for an overview, see [Goldberg, D.P., Huxley, P., 1992. Common mental disorders: a biosocial model. Routledge, London; Zuckerman, M., 1999. Vulnerability to psychopathology. American Psychological Association, Washington, DC.]). The predictive ability of vulnerability factors (the personality characteristics mastery and neuroticism) and stressful life events and their interaction was tested for an increase in general negative affect, decreased positive affect (PA), and increased anxiety. More specifically, we tested the hypothesis that loss leads to decreased positive affect in subjects with low mastery, whereas threat leads to anxiety in subjects with high neuroticism. Methods: Data from the Longitudinal Aging Study Amsterdam (LASA) were used. LASA is a longitudinal study in a large representative sample of adults aged 55 to 85 (N=1837). Self-report data on depression, anxiety, and negative affect were collected from adults over a 6-year period in three waves. The data were analyzed using multilevel analysis. Results: The findings revealed an association between low mastery, high neuroticism, and an increase in negative affect, lack of positive affect, and anxiety. Furthermore, high mastery protected against the negative impact of loss events, but neuroticism did not augment the negative impact of threat events on emotional health. Conclusion: Partial support was found for a diathesis-stress model of change in emotional functioning in late life. Furthermore, support was found for distinguishing between symptoms of negative affect, depression, and anxiety.