This research investigated the relationship between ego development and social network structure in grades 9 through 12 in a private school. Students filled out a sentence completion test for ego development and named friends with whom they spent the most time in school on a sociometric questionnaire. Popularity, mutuality in dyads, and choices among friends in triads were expected to be high at middle range ego levels and low at the higher and lower ego levels. Choices between cliques were expected to be low at middle range ego levels but high at the higher and lower ego levels. Results supported the hypotheses for girls only, suggesting a sex difference in the importance of network structures for personality development. Girls at the highest stages of ego development also had unique roles as liaisons between cliques, while having fewer mutual friendships in dyads. These results challenge the assumption that increased interpersonal mutuality always accompanies personality growth and suggest that, under certain circumstances, imbalance in dyads facilitates the integration of larger network structures. (Author)