Clinical material from the analyses of young children may be particularly useful in understanding the vicissitudes of the aggressive drive. In this paper, the psychoanalytic work with Teddy, a boy with aggressive and angry behavior, is presented to illustrate several important, intertwining and determining factors involved in the expression of his aggressive drive. These include traumatic events, his relationship with his parents and his dread of the strength of his instincts. When the child's experience includes the lack of external control of his impulses, he may be more predisposed to violent behavior. The importance of the stage of ego development at the time of trauma is also emphasized.