Several researchers in the 1950's proposed that hypernatremia causes water to leave brain cells, shrinking the brain, thus tearing the bridging veins and resulting in subdural hematomas. Although the old literature suggests mechanisms linking the two in a cause and effect relationship, there is controversy as to whether hypernatremia leads to subdural bleeding or whether the reverse is true. This issue is important for forensic pathologists who must distinguish natural disease from trauma. An etiologic link between hypernatremia and subdural hematomas was suggested recently, and was proposed originally before Kempe's 1962 paper “The Battered Child Syndrome” which widely disseminated the concepts of child physical abuse, and of subdural bleeding resulting from non-accidental injury. Our study is a multifaceted investigation of infants which includes: a literature review, retrospective chart reviews of both living and deceased hypernatremic infants, a retrospective review of infants hospitalized with subdural hematoma, and a prospective collection of head injured, hypernatremic children. We conclude that hypernatremia, if present in association with subdural hemorrhage, is most likely secondary to intracranial pathology, and that hypernatremia often develops in critically ill infants suffering from a variety of medical conditions.