Abstract This research explored four empirical questions: (1) Is self-esteem a better predictor of academic success and adjustment than other aspects of personality? (2) How is self-esteem related to Big-Five dimensions of personality during the transition from middle school to high school? (3) Do dispositions like Agreeableness or Openness relate to an adolescent's adaptation and affect reactions to the self? and (4) Do sources of information about adolescents (e.g., self-rating, other rating, objective “life history”) converge? We also explored the general hypothesis that personality, self-esteem, and teachers' ratings of adjustment during the middle school years predict later life outcomes during high school. Overall, results indicate Big-Five personality characteristics were more stable than self-esteem across this transition period. Agreeableness and Openness assessed in middle school are related to later scholastic competence and behavioral conduct, academic success, and adjustment in high school. Results were discussed in terms of personality development and self-evaluation.