This study was conducted to determine the frequency of abuse and neglect among infants and preschool children seen in the emergency department of a large children's hospital. A case-finding system was introduced using a checklist (Accident-SCAN) to remind the attending nurse and physician to consider the possibility of maltreatment in the etiology of each apparent accident. Thirty-nine of 2,211 accident patients were evaluated systematically during an 18-week study period and referred to a child protection team for investigation. Twenty-eight (1.3%) were presumed to be victims of abuse or neglect. This figure differs substantially from the widely quoted estimate of 10%. The marked discrepancy between this result and previous findings suggests that either important variations exist in the rates of abuse and neglect in different populations or that the earlier figures are overestimates.