Head injury in the youngest age group is distinct from that occurring in older children or adults because of differences in mechanisms, injury thresholds, and the frequency with which the question of child abuse is encountered. "Shaken baby syndrome" has results in intracranial and introcular hemorrhages with no evidence of external trauma. The cause of these injuries is vigorous shaking of an infant being held by the chest, shoulders, or extremities. Severe head injuries commonly diagnosed as shaking injuries require impact to occur and that shaking alone in an otherwise normal baby is unlikely to cause the shaken baby syndrome. "Shaken impact syndrome" has the advantage of being more inclusive of verifiable impact mechanisms and of reflecting the extreme forces that appear to be necessary to produce these often devastating injuries. All clinicians must recognize the wide spectrum of injuries in child abuse to ultimate protect the victim or other children in an at-risk situation. And physicians play an important role in diagnosis, management and prevention of child abuse and shaken baby syndrome.