Eleven participants carried out a study of aggression by utilizing clinical data from the analyses of patients who manifested significant problems in the management of aggression. The purpose of the study was to increase understanding of the intrapsychic factors that determine the nature and intensity of aggressive tendencies, the place they occupy in the psychic economy, their patterns of expression, and the extrapsychic factors that trigger them. The findings of the study indicate, first, that aggression is multiply determined by developmental, genetic (experiential), and dynamic variables; second, that each cluster of variables affects the nature, intensity, and expression of aggression in a fairly specific way; third, the importance of aggression in the psychic economy is proportional to the extent to which it is overdetermined. The successful analysis of aggressive individuals depends not solely on interpretation and insight, but on the relationship to the analyst as new parent who does not threaten and prohibit. The relationship to the analyst permits developmental change, particularly the ability to organize, structure, and control aggression. As a result, it need not be expressed destructively, but may be placed in the service of constructive thought and action.