Objectives: Existing studies in the Eriksonian tradition found that ego integrity and despair are important indicators of life-span development. The present study relates ego integrity and despair to contemporary theories of personality and mental health. Method: A cross-sectional study of Dutch adults aged between 50 and 95 years (N = 218) was carried out, using the Northwestern Ego Integrity Scale, the subscales for neuroticism, extraversion, and openness to experience of the NEO-FFI, the Mental Health Continuum-Short Form, and the Center for Epidemiological Studies Depression Scale-Short Form. Results: Extraversion and openness to experience have an indirect relation to ego integrity that is mediated by well-being. Neuroticism was related to despair and explained the relationship of depressive symptoms to despair. Chronological age did not moderate these findings. Discussion: Ego integrity appears to be related to fluctuating states of mental health, whereas despair is more an expression of a general trait-like disposition of neuroticism. Implications for further research are discussed.Keywords: Depression-Despair-Ego integrity-Erikson-Mental health-Personality-Well-being Ego integrity and despair form one of the fascinating conceptual pairs that Erik Erikson coined in his theory of human development across the life span. In contrast to identity versus role confusion (Kroger, 2007) or generativity versus stagnation (McAdams, 2009), it has not been the subject of intensive empirical research. Existing studies have mainly been carried out in the Eriksonian tradition, relating ego integrity and despair to the resolution of earlier psychosocial crises, to the acceptance of the past and the finitude of life. The present study addresses ego integrity and despair from recent theories of personality and mental health to bring it closer to contemporary psychology. We use a cross-sectional study of Dutch adults in their second half of life (50-95 years) to assess hypotheses derived from this broader framework. We are especially interested how ego integrity and despair are related to more stable dispositional traits as well as to mental health as a more momentary and fluctuating state.Erikson (1950, 1982) distinguished eight phases in his model of life-span development, each of which is characterized by a particular psychosocial issue. The last phase of life is characterized by the duality of ego integrity versus despair. Erikson described ego integrity as "the acceptance of one's one and only life cycle as something that had to be" (1950, p. 268) and later as "a sense of coherence and wholeness" (1982, p. 65). At the same time, late life brings reasons for experiencing despair, such as aspects of the past, present, and future that are difficult to integrate into a meaningful whole. Late life is therefore characterized by both integrity and despair as alternating states that need to be balanced.