Five infants, all less than 1 year of age, were killed by children 8 years old or younger. All five died from craniocerebral trauma resulting from assaults with a blunt instrument, being dropped to the floor, or both. Two had been bitten by their juvenile attackers. None of the victims showed any stigmata of adult "battering" in the form of multiple, nonlethal metasynchronous trauma, and adult involvement in the fatal terminal episode was excluded by thorough police investigation. The delicacy of the soft and bony structures of the infant's head renders it vulnerable to mortal trauma at the hands of tiny assailants. The preschool child is capable of homicidal rage when he is provoked by what he considers to be a threat to his sense of social security in his family unit or immediate human environment.