Self-esteem as measured by the Coopersmith Self-Esteem Inventory [Coopersmith, S. (1967),The Antecedents of Self-Esteem, Freeman, San Francisco] and ego development as measured by the Washington University Sentence Completion Test [Loevinger, J., and Wessler, R. (1970),Measuring Ego Development, Vol. I, Jossey-Bass, San Francisco] were evaluated in three groups of early adolescents: diabetic patients, nonpsychotic psychiatric patients, and a nonpatient group of high-school students. We found that low levels of ego development were associated with low levels of global and domain-specific self-esteem in all three subject groups. Levels of self-esteem among diabetic patients were not significantly different from those of nonpatients. While psychiatric patients had significantly lower self-esteem levels than the other groups, this difference was accounted for by preconformists, i.e., those at the lowest stages of ego development. Psychiatric patients reaching higher ego levels showed self-esteem levels indistinguishable from those of the diabetics and nonpatients.