Acting out by adolescents, often dramatic, has been proposed by Blos, Winnicott, Erikson, and others to function in the service of development. The author uses the ego-developmental model of Loevinger to analyze the meaning of acting out in the cases of three adolescent patients and to describe differences in therapeutic approach based on the model. In the "preconformist" stage the individual "gains a sense of self from feelings and immediate perceptions." Objects are regarded as sources of gratification, frustration, etc., rather than as separate individuals. Family therapy may be the most effective treatment modality at this stage. In the "conformist" stage reference group membership defines the self. Conjoint therapy rather than individual may still be the most effective. The final "postconformist" phase brings a greater sensitivity to individual difference, an awareness of separateness, a capacity for insight. Even with an adolescent who at times acts out in a regressed manner, psychoanalytic psychotherapy becomes possible if the postconformist phase has been attained.