In this paper, we review findings from Project Competence on the nature of personality development from middle childhood through the early adult years and place these findings in the context of current research on temperament and personality traits. In a series of studies using data drawn from the Project Competence longitudinal project, we have addressed a set of fundamental questions about personality development: What form or structure do personality differences take in middle childhood? To what extent is there continuity or change in youths' personalities over time? Do children's personality differences predict their mastery of developmental tasks in childhood and adulthood? In this paper, we review the findings for four middle childhood traits with significant overlap with four of the Big Five traits--Mastery Motivation (Openness), Academic Conscientiousness, Surgency (Extraversion), and Agreea-bleness. Adopting a "personality perspective" on children's traits has yielded important insights into the patterns of individual lives over time and should prove helpful in future work bridging the gap between early childhood temperament and adult personality.