This study introduces a measure of introspectiveness for adolescents aged 12-18 and investigates its association with several aspects of adolescent development. Introspectiveness-the tendency to deveote diffuse attention to thoughts and feelings about the self-increased during adolescence, and may be stimulated by discontinuities associated with adolescent development, other kinds of discontinuities, and parental introspectiveness. Also, introspectiveness was positively associated with depression, anxiety, and physical symptoms, and may help explain the increase in symptom reporting during this developmental period. Highly introspective adolescents participated in more artistic activities and spent more time alone than those low on introspectiveness. Finally, highly introspective college students chose self-oriented academic majors, which may have implications for future occupational development. Together these results suggest that the concept of introspectiveness may increase our understanding of several important aspects of this developmental period.