Developmental changes in self-perceptions were studied in children and adolescents in grades 4, 6, 8, 10, and 12. The responses of subjects to the question Who am I? were analyzed by means of a 30-category scoring system. Children described themselves in terms of their physical appearance and their behavior, while adolescents referred to their beliefs and their interpersonal style. Few sex differences were noted. Adolescents did not use more categories than children; they used different categories. (Author/ED)