In this paper the author describes the significance of adolescent personality in the formation of mature adulthood. Adolescence is the phase of life in which the individual develops a great ability to sublimate. The ego ideals of the adolescent are invested with a great amount of narcissistic libido, and a pessimistic attitude toward the ideals of youth can result in serious personality disturbances later in life when a relatively mature adult should remain loyal to his ideals but be able to alter the means of realizing them. In general the writer does not believe that a patient's childhood conflicts can be analyzed without a thorough understanding of the identifications and displacements which occurred during adolescence. Four case histories are presented which show that disturbances in adolescence due to conflicts between goals and methods of achieving them prevented maturation.