Preoedipal play between two fathers and their sons, which had permanent effect upon the children's subsequent development, is described. In one case, the father had accepted 'victory' over himself by his son only to 'defeat' suddenly the child by screaming at him and then forcing him to stand motionless for a long period. In later life, the son showed a repetitive sequence of omnipotent victory followed by annihilating, self-inflicted defeat. In the other case, the son later in life withheld desired objects from his daughter until she screamed violently, whereupon he would give her the object with an approving smile for her persistence. He was an overaggressive person who had been encouraged by his father to behave like the daughter, and then allowed to win. In both cases the mothers had not been able to participate consistently and favorably in their sons' subsequent development.