In psychodynamic psychiatry and psychoanalysis, the concept of ego development is important for both clinical and theoretical work. It has been difficult, however, to derive techniques which meaningfully measure ego development for use in clinical research. The Loevinger Sentence Completion Test has been found reliable and valid, but no study has shown it directly pertinent to clinical perspectives. Our research investigated clinically relevant correlates of ego development, using the Loevinger test followed by videotaped interviews of ninety-eight adolescent girls, to discover how certain character styles predicted to be associated with different ego levels would be expressed in interpersonal interactions. Our results were consistent with clinical and theoretical descriptions of adolescents from varying ego development levels. These findings emphasize the relevance and usefulness of the ego development measure for clinical research and studies of the life cycle.