Now in a revised and expanded second edition, this influential work argues for the enduring stability of personality across adult development. It also offers a highly accessible introduction to the five-factor model of personality. Critically reviewing different theories of personality and adult development, the authors explain the logic behind the scientific assessment of personality, present a comprehensive model of trait structure, and examine patterns of trait stability and change after age 30, incorporating data from ongoing cross-sectional and longitudinal studies. The second edition has been updated throughout with the authors' new findings, ideas, and interpretations, and includes a new chapter on cross-cultural research. It culminates in an additional new chapter that presents a comprehensive theory of personality grounded in the five-factor model.